To start off, here's a quick overview of the parts of an accordion and list of its functions.
Got your accordion? Good, unless it's a concertina because these would not apply to you. Now please take a seat, wear the straps and position the accordion in a way that the treble part is at the center of your body and the grille is sitting on your left knee. Make sure not to let the bellows snag onto anything because it would eventually get damaged and you'd have a hard time pushing and pulling.
And here's a bass button reference for your possibly chromatic accordion in the Stradella system be it piano or button. Click the image to download!

Everyone says you should get an actual tutor so that they could tell you what you're doing wrong and stop you from forming bad habits but sadly not everyone has access to one. As I am not really equipped to teach (I'm learning myself, haha), here's a list of links to people who are very good at it and plus, all for free!