I would just start with some basic things, perhaps make some cloth wipes etc, and play with the different stitch settings that way you can see what each dial does and that way you get an idea on where to start, and it won't matter if they are all "perfect" IYKWIM It is great to as it cuts as you go, so you cane make nice rounded corners without have to precut the round corners as well

Also you can do a rolled hem, but removing one of the threads (I think it is one )

The best way of re-threading with different colours is to tie the threads together, rather than threading from scratch as some of the threads are a real pain in the bum to have to rethread each time

Also look on you tube and see if there are any demos on who to use the machine that you have purchased, and if all else fails, round Maz up and get some lessons

Have fun though, overlockers are sooo much fun, hoping to inherrit my mums when she buys a new one