If the cranks are properly aligned with the spindle, the cotters should fit in by hand and
seat themselves about 1/2 way in. Then use the press (or hammer) to fully drive them home.
Not sure about your hub...
You should back off the non drive side cone and then tighten the drive side cone (finger tight)
Hub adjustment is then completed by tightening the non drive side (finger tight) and then
backing off perhaps a 1/4-1/2 turn to allow for play.
Once installed with the chain attached, the non drive side can be further adjusted.
Ideally the hub should spin freely with little or no spinning of the crank and a little
side to side play of the hub.
It's all a matter of "touch".
https://www.youtube.com/watch?v=vNxwMwzS3Jo
Over tightening the hub can mess up the innards...