On topic, to have a prepared weapon you must enter the 'e'quipment screen and press the letter next to prepared slot (can't remember what letter is right now). You will be prompt to take a weapon from your inventory to put on that slot. You will then be able to swap quicker between you main weapon and your prepared weapon than swapping between main weapon and a weapon in the inventory. This can be accomplished with the letter 's', if I remember correctly.
The other way to get a prepared weapon is to press z, equip another weapon, and press z again. Z, by the way (*looks at Adral*), is the default prepared slot switch key. Juggler only lowers the amount of turns it takes to switch weapons, and compared to traits like Eagle Eye and Ironman, which will directly improve your combat survival chances, is really not useful at all.
and how do I know what level I'm playing and how to switch it?
I assume you mean difficulty level. This is chosen right after you select New Game, and the levels available from the beginning are I'm Too Young To Die (ITYTD/Easy), Not Too Rough (NTR/Medium), and Hurt Me Plenty (HMP/Hard). You can also unlock (with further play) Ultra-Violence (UV) and Nightmare! (N!) difficulty. You can't change your difficulty after picking one, so you should choose wisely. I'd recommend sticking with ITYTD until you're able to finish it (or one of the special challenge modes) since even that can be rough for the uninitiated. Of course, if by level you meant "level of progress"/"level of the game" or some such, then you can tell that by looking in the lower-right corner and change it by going down a set of stairs ;).
Congrats on getting to level 7, though.
