Pick a hero that you will want to play. Personally I like the guy with the axe because I feel he does more damage. Press E to show your cursor and move your skills down to the hot-key bar so when you press the number 1 and 2 keys it will use those skills on demand. Run around the first level and hack and slash down 50 zombies and then you will need to look for a portal to move to level 2. Once you find the portal press E to show your cursor again and click the Let's Go button.