If your Instagram post will be an image with the type Feed, it's possible to tag other public Instagram accounts on a picture. To do this, follow the steps below:
Click Social Campaign Summary, then click New Social campaign.
Give your social campaign a name and select the relevant social pages.
From the Placement list, choose Feed.
From Post Details section, click Media
then select Add Image.
Click on the three dots next to the image, then select Tag image.
You’ll then be able to click anywhere on the image to tag the desired public Instagram account.
Once you’ve made the desired tag and saved the post, the image will be shared with the tag linked to the Instagram account you wish to include.
📌Note: Instagram API does not allow searching for usernames, and tagging private accounts will not be possible.