Step 1: Go to the Google Play Store or App Store. Step 2: Click on the search bar. Step 3: Enter "Call of Duty: Warzone Mobile" in the search bar. Step 4 Click on the game Step 5: Click on "Download" or "Install". Step 6: When the installation is complete, enter the game. Step 7: There is going to be a text saying "Update Required" and there will also be a button called "Download Update". Step 8: When the update is complete, there will be 3 buttons "Sign in", "Guest", and "Go back". Step 9: Click on "Sign in", or "Guest" (Optional) Step 10: When you click "Sign in" or "Guest", for guest there will be a screen and text which says "Enter your Username", and a text box, click on the textbox and enter the username of your choice, after that, click on "Continue", and you should be in, if you click "Sign In", you will also be on a screen with text called "Enter your Activision Account", and 2 textboxes, the first textbox requires your email address, the 2nd textbox requires your password, and you are in! Hope this helps!