Please keep in mind that you can not claim an Instagram account you do not own. If you are advertising on the behalf of another person, the owner must initially claim their Instagram account through their own Facebook Organisation Manager.
How To Link Instagram And Facebook
If you own the Instagram account: Just go to your Facebook Service Manager and click on settings. Under the People and Possessions tab, click Instagram Accounts on the left then click Claim Instagram Account button on the right.
Type in your Instagram username and password.
You can also opt to link it to your advertisement account if you have one.
Furthermore you can also assign partners to handle your Instagram account after you've link Facebook Business Manager to your Instagram account.
Back in the ads manager page, as soon as you have actually effectively added the account you'll have the ability to choose your Instagram account at the advertisement creation page.
Doing this will enable people to click to follow you on Instagram instead of sending them to your Facebook page.
Bear in mind that you can not directly buy followers on Instagram as opposed to Facebook likes campaign How To Link Instagram And Facebook.