Absolute Beginner, Read the Rules, still confused!

[shoggoth]

Ok.

I'm a camp counselor at a Lovecraft live action role playing camp for kids. For the camp I bought Munchkin Cthulhu having never played Munchkin before in my life. I really want to get into it, but darn it despite having read the rules and looking on youtube I can't seem to get a straight answer on the very first problem, even the flash how-to doesn't address this issue!

In the beginning of the game you get 4 cards from each deck. If you don't have any items you can use or play do you have to just discard cards until you get down to 5 cards in your hand? You're meant to only have 5 in your hand I get that. Can you just randomly discard anything to make room for, say, a three-barreled shotgun or another useful item to come?

for example: I tried to play a mock game with myself to start and my first draw was 4 monsters with level 12 and higher and a couple of curses and items I couldn't use. I sat there like an idiot not knowing what I was supposed to do with 8 cards I couldn't use when I'm only supposed to have 5! Do I discard until I get down to 5 cards?

I have a few more questions but this is the first big noodle-cooker of the game. If I can't figure this out I can't even begin to move on to the next questions!

THANK YOU!!!