There are many ways to earn money online, one of which is app monetization.
This method is very easy to practice to earn money. Please visit the admob website, this is a product from google, who can I join as an admob partner.
Register the contents of the data as requested by admob, after the account is approved then you can create an ad code to run on the application.
If the ad code has been installed in the application, then the next task is so that many applications are downloaded so that they make a lot of money from the ad earlier.
Please practice to create an admob account, even though you don't have the application, it's not wrong to create an account first, if you want to make a free application, many websites provide free applications.