The game is in its very early state, so if a question is not listed in here, chances are you cannot do that yet.
See the Planned Updates page to see if it's planned. Otherwise, feel free to drop an issue at the GitHub page. Don't mind the one issue that's been there forever.
The spawner might be off. Click on the square in the top right of the enemy tab. If it's green, that means the spawner is enabled. You might also have hit the max enemy count, which is 3. Right-click an enemy to remove it.
To battle an enemy, click it. In battle, each turn, both you and the enemy attack. They have a chance to attack and miss, which is determined by the accuracy stat (an accuracy of 75 means you have a 75% chance to hit). If you hit, you damage the other team by your attack stat minus their block. If both sides reach 0 HP, it's a tie.
Some Buffs may interfere with the battles, for example Health Potion which has a chance to heal you on a turn. All of them also trigger every turn, so Health Potion for example might heal you or make the attack weaker.
Technically, it never ends, but the end of content for now is getting all 4 Buffs.
There are three: Red Square, Green Square and Blue Square. The Blue Square is the strongest, and usually requires a few buffs to beat.
To be honest, making area names was a mistake. I literally can't think of any title.
They aren't instant use. You have to go into the feature that it's related to and use it there (so Enemy tile for Square Spawn and RBU tile for RBU Recharge).
They don't stack yet, so if you select the same Buff in a RB, you're effectively wasting 45 RBU. However, a later update will add leveling up Buffs, so it won't be useless.
There are currently 4 buffs: Sword Plushie, Heart Plushie, Health Potion and Target Plushie.