First of all - Make sure that you are an Administrator (full control), if not, please share this guide with the right person in your team.

In your Google Ads account, click the Admin icon

Click Access and security

Select the Managers tab. Under “Link request”, you’ll find a list of manager accounts that have requested to link to your account

In the "Actions" column, you can Accept or Decline an invitation by pressing the corresponding word.

To complete the action, follow the instructions on the page.