People keep wording this question in different ways. I'm not sure if they're wondering how to use the items they've downloaded in game, if they can't figure out how to spawn them when in game, or if they're just wondering where a list of everything is. To try to help out, I've made a screenshot tutorial that should HOPEFULLY answer all of this. If this isn't the issue you're having, please elaborate and I'll see if I can answer that question too.

First thing you'll want to do is go to the object creator. Go in game, and hit the glue and scissors in the upper right. I put a red arrow under it for clarity:
http://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=110229915

This will bring you to the editor. The first tab will have items that have been created by yourself. The tab you're looking for is the one to the right that has all items that you have downloaded. Click the blue Steam Workshop button that you can see here:
http://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=110229948

Find the object you like, and click on it in the list to bring up it's main page. Sup Deadpool, how ya been, buddy? I found him on the first page, so decided he'd help me out for an example. Click on the green "Subscribe" button you can see below and press Shift-Tab to get back to the main game:
http://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=110229973

Now wait a moment. In this instance it took about 45 seconds for him to appear, but eventually, there he was. You can go ahead and keep adding various items in this manner without Shift-Tabbing every time, but I've found the only way so far that always works for me is to go into each page and subscribe to them there. Doing it from the list view has sometimes not worked, and I have never got it to work while subscribing out of game and then loading it up.
http://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=110230000

Alright, let's invite Deadpool over to the farm and see how it goes. Same process as any other object now. Bring up the notebook, type "DEADPOOL" and hit enter, and drop him in:
http://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=110230055

Looks like they're getting along juuust fine!

Thank you Veen. I didn't know you needed to add items from in-game

hey! thanks so much...knew there had to be a way

now, what if, like me, the blue Workshop buttons don't actually DO anything? I click them and it doesn't bring me out of game and into the Steam Workshop.

Are you sure you have selected the download tab first? On the 'my design' tab, it is used to share your own designs.

I click the blue workshop button, it takes me to the overlay with the web browser thing popped up, but the page never loads. How am I supposed to get the items I've subscribed to out-of-game to work?

Is there any way to make these objects into an avatar?

I can't click on the object creator, it seems disabled. how do i fix it?

You need to download ingame andd it works...

a

awts. i thought i could play as them. hehe.

you can just move the green boxes to bove body parts. I'm going to make a mega man avatar

引用自 Undertaker：

I can't click on the object creator, it seems disabled. how do i fix it?

I have that same problem. I can't figure out how to fix it, it says to open steam and restart your game so I do nothing happens.

how do i make object creator available?..im not able to even open it

yes you have to be in game and then subcribe to content