Below are the instructions I give my clients when I am creating an ad campaign or adding a remarketing pixel to their 22Social app. These instructions can be found in Facebook Help but I have found that the graphic I created really helps my more visual clients get it done easier.
To give another Facebook user access to your advertising account, follow these steps:
2) Scroll down to the Ad Account Roles section and click Add a Person (a small window will pop up)
3) Enter the name or email address of the person you want to give access to.
4) Use the dropdown menu to choose the role you want to assign them. You can learn more about the different kinds of advertising permissions here.
5) Click Submit.
Note: Adding people to your advertising account doesn't give them permission to log in as you or see things on your profile or Timeline that you haven't shared with them.