Weld issue

Maybe this is not the place for these kind of questions, but i've started mapping, but i can't see to weld faces togheter.
I select the two faces i want to weld and either options of welding (- near vertices and - selected vertices) doesn't work.
Can someone help me to tell how to weld two faces togheter? Because i want to similer shapes at either side of the ready room.

(why can't this be like solidworks =( ?)

Many thanks in advance cause i got this great idea for a map.