Your character gains XP for every kill you perform. There is nothing you need to do specifically for this as you will reach level 5 for your character before you reach Zone 10 on your journey.
Note that you level is in a single run so doing a ritual (essentially a reset) before you reach level 5 means you'll need another run to attempt it again.
TLDR: Sit back, watch the screen, don't do a ritual, and you'll get to level 5 along your journey to Zone 10.