Question about this press I bought and reloading help

[Bumpy]

A few months ago I purchased this Bair Company press for 10 bucks. My question is this primer piece that is on the side how does it work?
So far I've only used a Lee Loader for my 308 ammo but I'm finally deciding to go with a full set up. Things that I know I need are a scale, bullet puller, and what else?

things that I have
1) Varget powder
2) bullets
3) dies I can get
4)electronic ruler to measure my rounds, case

[M16]

When you run the case in the size die at the top of the stroke push the primer ram in. One the downstroke you seat the primer. I would use a Lee hand primer instead.

[Bumpy]

Thanks that seems safer as well