how to make a platform game for hordes

good as the title says I'm looking for ways to make a platform game and what I want to know is how to schedule an event in which the number of enemies increases.

You can use the "Every X seconds" condition on System (Add Event > System > Every X seconds) to create some kind of enemy waves (spawn new enemy every 5 seconds for example). Or if you need increasing number of enemies, you can use a variable to keep track of how many enemies you want to spawn at once.

For how to spawn an enemy, you can use the "Create object" action on System.