In this section you will learn on how to get the items that you need, right now its the satchel charge. Even if you have the satchel charge, read this part anyways.
1. Open the console (If you don't know how to do that, theres plenty of other guides)
2. Type in "sv_cheats 1" , "impulse 101" and "buddha" (Without the " things)
3. Now you should have the weapon - the satchel charge (And a few others). The satchel charge is in the "specials" section where the grenades are. (The buddha command gives you the ability to not die, you can still loose hp down to 1 hp but then when you have 1hp you're invincible)
4. Open the console again and type in "bind n givecurrentammo" (Without the " things)
5. Now, when you have the weapon you should be able to just press n and get more satchels!

Now, that you got the weapons you will need to :
1. grab the satchel charge weapon and hold down your Mouse2 button (Right click).
2. Spam the n button so you'll get more ammo.
3. Keep doing this until you got a wall.
4. Detonate it and feel your eardrums explode .