How do i change weapons

[:1]Ive been playing the singleplayer and i just picked up the rocket launcher, however its **** so i went to the workbench and tried to reequip my assualt rifle and just realised i had no idea how. I have tried tab, drag and drop keyboard bashing but no luck. Im sure theres and obvious answerand i was probbally told earlier in the game but i cant remember and i cant work it out. So please help me|||just click on one of the two weapon slots on the bottom left and all the weapons you found should pop up on the bottom (you may have to click and hold). choose one.