Sign out of all Google accounts in your browser or app
Go to Google.com and sign in with the account you want to use first
Add your other Google accounts after signing into the preferred one
On desktop, make sure the preferred account is the first one signed in
On mobile, set the preferred account as the primary account in the device’s Google or Gmail app
If needed, remove all accounts and sign in again in the desired order
For Chrome, sign into Chrome with the preferred Google account first
Refresh the page or restart the app after changing the sign-in order