We will have a draft, that functions much like the regular one, and each of us will get to pick what players we have on our team. RBs and WRs tend to be the flashiest and first players picked, as well as QBs. These three positions earn a good amount of the points and are therefore valued the highest.
Each week you will set your roster, according to the roster setup the league goes with. Say you have Tom Brady as a QB, and the Bucs are playing a team with a poor passing defense. Well you will want to make sure that Tom Brady is your starting QB, although you will usually have a backup QB as well... You can play either, you just want to play for good matchups.
Say Tom Brady throws 250 yards and 2 TD's. Well the league will set up scoring rules. So at 1 pt per 25 yards, and 4 pts for a passing touchdown, Tom Brady will have scored you 18 pts. Some leagues do points per reception, points per completion, every 20+yard play is a point, etc. You can really customize this which is one part I really like doing. And so each player you start for the week will win you points depending on how good they perform. Each week you will be playing another team, say it's wk3 and it's neversickanymore vs. mal3volent... Well if nsa scores more points he will win, to put it simply.
That is at least a barebones basic guide to it, but I'm happy to discuss it more if anyone has any other questions, there's a lot of learning that goes into it, even for me and I've played many leagues over the years. It's really only been the past couple years that I've done my own league, but I've had two years running my own league, this past year I skipped though just due to all the turbulence in my life. Really quite a bummer because it was a good year of football.