Stick Hero 3 is an idle game. That means you have to do nothing to make progress in the game - although you should improve and upgrade your character while you play, with upgrade points for example. Sometimes surviving in a new zone is possible only by being active (using potions and spells etc).
When you begin SH3, you must choose your character class and autosave file slot, or load an existing character from a previous file slot. You can have up to three characters saved at any time. Once you create a character, your adventurer will appear in The hills and you can begin exploring.
The gameplay is similar to many other idle games, just like Stick Hero Idle 1 and 2. You walk around different zones and encounter monsters which your character fights. If you win, you gain experience points and money. If you lose, you die.
Like most idle games, SH3 also has anti-idle features which mean things you need to actually 'do'. You can't let the game do it itself. These include spells, potions, Spukkit Coin picking, Game Hall etc. These are not necessary, but most of them improve your gameplay greatly.
The Cellar area has a 25k hp monster, the Invisible giraffe, which drops 4k spukkit.....you can typically make 80k an hour doing this process. You can idle here when the monsters start hitting 0's on your character....most easily done on the knight since high defence. This is a very easy way to make the extra spukkit for that mega package :D