Open the Gmail app.
Find settings, and press Add Account, or Add an email address
From the list of available account options, choose Other.

Enter the full email address you are adding, then tap Manual Setup.

Select IMAP from the list of options.

Enter the password for the account you are adding, then press Next.
On the next screen, ensure your Username and Password are filled in correctly.
In the Server section, enter your server information as provided. If you’re not sure what this is, get in touch. Tap next.
On the next screen, ensure the Require signin toggle is slid to the right. Also, check that your Username and Password are filled in correctly.
In the SMTP Server field, ensure the SMTP Server is set to the details provided. If you’re not sure what this is, get in touch. Tap next.
You’ll briefly see a screen saying Verifying Account Information and then, if the information you entered was correct, you’ll see a screen like the one below. The default settings should be sufficient. Tap Next

On this screen, you can give the account a name, which is super useful if you have multiple email accounts setup in the Gmail App.
Under Your Name, ensure the name you want others to see when you send email on this device using the Gmail App is set appropriately.
Tap Next when ready, and your inbox will setup.