First, you need to be in a Coalition with them. After that, the Federation Council meets every two years (usually around February, if memory serves). During the meeting, the option to invite powers into the UFP should be at the top (again, as long as you're in a Coalition with them). From there, you have the option of opening low, medium or high-level negotiations, each of which costs a higher level of Influence (except low level, which costs none). Obviously the smaller powers (e.g. Denobulans) take less time and influence, while larger powers take longer and more.

The hardest issue, naturally, is getting into a Coalition with the powers you want to integrate. I admit I've had to resort to console commands to jump into another NPC power (like the Trill), get them to dissolve their Coalition with the Ferengi, so then I could snap them up. I hope this helps!

What about the ones that aren't FTL though, like the Axanar or Centauri?

I want to bring as many into the Federation as possible. From the Denobulans to the Centauri to someday even the Klingons

引用自 tilarium：

What about the ones that aren't FTL though, like the Axanar or Centauri?

That's a bit different. After you construct an Observation Post in their system, you'll have the option upon clicking it to integrate them into the UFP. It takes a while, and costs 1 influence. But I'm fairly certain that, as long as their warp-capable, you should be able to integrate them. To be on the safe side, maybe enter into diplomatic relations and select 'The UFP would welcome you as a member.' If the option to integrate isn't naturally present, it should show up now.

I think something might be broken here. I went to invite the Centauri people into the UFP but couldn't. They want me to build an observation tower first. There is already an observation station in orbit of the planet. Is it something else that needs to be build or could it be because the station was build long before the Federation was formed?

https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=3229077353

引用自 tilarium：

I think something might be broken here. I went to invite the Centauri people into the UFP but couldn't. They want me to build an observation tower first. There is already an observation station in orbit of the planet. Is it something else that needs to be build or could it be because the station was build long before the Federation was formed?

https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=3229077353

So when you click on the Observation Station in the system, you should see the usual options--in the Fed's case, passive influence only. But right next to it, do you see a UFP emblem? Highlighting it should give you the option to integrate the Centauri into the UFP, at the cost of 1 Influence per month until it's done.

https://psteamcommunity.yuanyoumao.com/profiles/76561198003519626/screenshot/2518150500896818844/

Only UFP symbol on there is the one in the top corner, which just takes me to my government screen.

EDIT: Ok, so there is something wrong with the observation post over Al Rijil. I just finished building one over Altair VI and it is looking like it's supposed to with the 4 options; Passive Observation, Aggressive Observation, Federation Membership and Activate Cloaking while Al Rijil has just 3 options; Diplomatic Embassy, Aggressive Observation, and Activate Cloaking. Not sure why it is like that. I even destroyed the station and rebuild it stayed the same. Very strange!

引用自 rocketman544：

First, you need to be in a Coalition with them. After that, the Federation Council meets every two years (usually around February, if memory serves). During the meeting, the option to invite powers into the UFP should be at the top (again, as long as you're in a Coalition with them). From there, you have the option of opening low, medium or high-level negotiations, each of which costs a higher level of Influence (except low level, which costs none). Obviously the smaller powers (e.g. Denobulans) take less time and influence, while larger powers take longer and more.

The hardest issue, naturally, is getting into a Coalition with the powers you want to integrate. I admit I've had to resort to console commands to jump into another NPC power (like the Trill), get them to dissolve their Coalition with the Ferengi, so then I could snap them up. I hope this helps!

I really do appreciate it; that nation is *VERY* unique in how it expands.