Automation in Homey is handled by so-called “Flows”.
A flow consists of three phases:
- WHEN - the part of the flow that controls WHEN or WHY the flow should start, eg. that a button has been pressed or an event has occurred.
- AND / OR - the part of the flow that checks IF stated conditions is fulfilled or not, eg. that it is a certain day or a device have a certain status.
- THEN / ELSE - the part of the flow that EXECUTES something, eg. lighting a lamp or calculating a value.
The three parts of the flow can sometimes feel narrow and limiting, but if you add the possibility of starting another flow based on the outcome of a flow then endless possibilities for custom flows are opened.
Aside the great flow topics on this forum Athom has a good beginner guide here that show how to create, modify, save and test flows: https://support.athom.com/hc/en-us/articles/360009669174-How-to-create-a-Flow-to-automate-your-home.
What can also be good to know is that you can enable/disable flows, this can both be done manually and from within a flow. A good example of this is to have holiday light flows automatically enabled/disabled based on time of the year.
Make a habit out of putting test flows as inactive so that they do not interfere with production flows. An inactive flow can be modified and tested without first being activated so this way you can avoid a lot of hard to find problems with devices acting strangely.
Good luck building your flows! Feel free to ask for help if needed and do remember to share your flows when you create that great solution! 
