Follow the below steps:
1.Visit ads.google.com and click Get Started.

2. Click on New Google Ads Account, with your existing logged-in Google account.

3. After that your account will be linked with Google Ads, complete the further set-up to run your ad campaigns.

Also Read-
How to add a partner/user in your Google ads account
How to create LinkedIn ads account
How to add a user to your LinkedIn ads account
How to create a Facebook business manager account
How to add a partner/user in your Facebook business manager account