Activating/Equipping New Weapons (Ripper, Flamethrower)

[mlm2.wordsmith]

So I've found the ripper and the flamethrower - was able to pick them up but can't seem to equip them for active use. They show up in my inventory, but I can't figure out how to assign them to the 3 and 4 key slots for weapons (1 and 2 taken with the plasma cutter and pulse rifle).

PC user, if it helps.

[Smetrix]

Navigate to one of the weapons in the inventory, then hitting enter should give you the option to equip it to a slot.