Click on your summoner icon in the top right, then select "Settings" from the menu, then select "Overlay" from the tab near the bottom left, and finally click the toggle to enable the overlay!
If the overlay is turned on but still not working, please check that
1. You are running both the app and game client as admin.
2. Antivirus or overclocking is not blocking the overlay
3. Other overlays are not blocking the Mobalytics overlay
If you have done all these steps and still do not see the overlay, please contact support or message our support team on Discord (https://discord.gg/r6XkVkGuUZ, Accept the rules in #welcome, then go to #user support) and we will help you! :)