You need to sell items; right-click (or hold) an item in your inventory to open a menu where you can sell items.
The free version includes the first four girls, with the next one unlocking upon reaching level 25. The full version from Patreon grants access to all the girls. The game features a special skill that performs automatic clicks during the mini-game; to learn more about the skill, simply press and hold it. The same applies to crafting.