Each Web Monetization micropayment increases your funds in the game. 100 micro-dollars ($0.0001) earns you 10 gold in the game.
You'll spend your money to grow an army of goblins. Try to make as many goblins as possible by the end of your 35 days.
To plant a goblin you can click anywhere on the green area. This plants a goblin, which will grow up and earn you some money when it's fully grown. Goblins cost 10 gold and earn 20 gold.
Once you have some more money saved up you can buy pentagrams. Hit `p' to switch to pentagrams (you can hit `g' to go back to goblins) and click to place a pentagram. Pentagrams stay around and produce goblins forever but they cost 100 gold. Each goblin they make is worth 20 gold.