Step 1: Go to "Marketing" and select the "Social Planner".
Navigate to Social Planner > Settings. Visit the overview and you'll see a Setting option (gear icon).
Step 2: After clicking Add account, there will be an option to add the Instagram Business Account.
Step 3: It will ask you to choose Facebook and provide Social Planner permissions. Use your Facebook account with an Instagram Business account connected to it, type in the necessary details, and click Log In.
Step 4: Next step is to select Instagram Business Profile(s), you wish to add to Social Planner.
Note:
Step 5: In the Setting icon, you can manage your accounts.