Log in to https://business.facebook.com and create an account, if you haven't already.
Once logged in, click on your business settings (top right)
Look for Ad Accounts on the menu that flies out.
Next, click on Partners and then Assign Partner
On the next screen, select the link Connect your ad account using your partner's business ID instead.
Under Role, select Ad account admin
Add in our Business ID: 629506900551583
If done correctly, you should see a page telling you you've succeeded.