The Social Campaigns tool is the best way to automate your Facebook and Instagram posts, with it you can create your posts, add them to campaigns you can then schedule for automatic posting, or just post right away with a simple click.
Requirements:
Facebook Business Page
Instagram Professional/Business/Creator account
Link the Instagram account to your Facebook Business Page
The key to making this work is tying your Instagram to your facebook business page.
Login to Facebook
Switch identity to the business page
Visit Settings > Permissions > Linked Accounts (https://www.facebook.com/settings/?tab=linked_profiles)
Next to instagram click view then connect
Find Facebook's official instructions here:
Backoffice Integration
Once you have your account linked as detailed above, here's how you can integrate your Instagram account with your Social Campaigns tool:
Go to Social Campaigns > Login > Change Auth or Authenticate.
If you have previously authenticated, you'll see the Change Auth button.
Otherwise click the Authenticate button.
This will launch facebook, which you must login to if you are not already.
If you've already authenticated previously, you'll see an "Edit Previous Settings" link on the first step of the Facebook login. Click that link to update your preferences. If not, simply proceed through the prompts as usual to grant access. One of the steps will include granting access to Instagram.
You will be able to start posting on your Instagram account once this process has been completed. You can post directly from the Templates area, but also start campaigns on your Instagram account(s).