When you have your inventory screen open you will see a little scroll in the top right corner of the inventory. You can click that to see you current player level and stats. From here you can increase some stats when you have points available.
The screen you will see when you first join.
If you click on the Shield icon you can see your resistances.
50% of the XP you gain from mining and slaying the beasts of the world will contribute to your level on this screen.
In the top left corner you can track the current season.