You have 2 options to link Gmail accounts to your iPad either through the pre-installed Mail app or by downloading and setting up the Gmail app.
To set up a Gmail account through the Mail app, access the "Passwords & Accounts" category within the Settings app on your iPad (A).
To set up Gmail accounts in the Gmail application, click on the "Sign in" button for your initial account, and proceed to select the account picture to add more accounts (B).
(A) How to add your Gmail account to your iPad Mail app
Open Settings.
Click on "Passwords & Accounts."
Click on "Add Account.
Click on "Google."
Enter your Gmail address and then click on "Next."
On the next page/step, enter your Gmail account’s password and click "Next."
Start the Mail app. You will see the Gmail account.
(B) How to set up Gmail account on your iPad through the Gmail app
If you have not yet installed the Gmail app, please proceed to do so. Open the App Store and look for Gmail. Once you locate the app, proceed with the installation on your iPad
Open the Gmail application. If this is your initial time launching Gmail and there are no Gmail accounts configured on the iPad, you must select "Sign in" located at the bottom of the screen.
Click on "Google."
You will see a pop-up window, enter your Gmail address and then click "Next."
On the next page, kindly enter your password and click "Next."
Once you have added your initial Gmail account, it is simple to include more accounts.
Within the Gmail application, select your profile image located to the right of the search bar, and then choose "Add another account." Proceed by following the provided guidelines to input your email address and password.