Here's the basic process for leveling up.
Proficiency Bonus increases at level 5, 9, 13, & 17
Consult Class in Players Handbook for additional features and Ability Score increases
Recalculate Ability Bonuses (Ability - 10)/2 round down + Proficiency Bonus
Gain 1 hit die.
Consult Class in Players Handbook for Max HP
Consult Class in Players Handbook for increasing Spell Slots
Familiarize yourself with the new available spells