Follow below mentioned steps to provide firebase account access :
Step 1: Go to Firebase
Step 2: If you have a Firebase account, Sign in, else Create an Account.
Step 3: Click on Get Started.
Step 4: Select the Firebase project for which you want to grant access or click on Add Project to add a new project.
Step 5: Click on the gear icon on the top left.
Step 6: Click on Users and Permissions.
Step 7: On the Users and Permissions page, click on Add Member.
Step 8: Enter the email address of the member to be added.
Step 9: Select a Role for the added member from the dropdown.
Step 10: Select Owner to assign a member the role of Owner, then click Done.
Step 11: Once done, click on Add Member.
Step 12: On the Users and Permissions page, you will see the added member and assigned role.