If a username you want is already taken and seems inactive, you can not do anything to get that username. A username once taken is taken unless Instagram itself removes them permanently. What you can do is, choose an available version of the username to use on Instagram. You can add periods, numbers, underscores or abbreviations to help you come up with a username that's not already in use.
You will have to edit your profile information to change the username. Here's how:
- Go to your profile by tapping the silhouette icon.
- Tap Edit Profile.
- Type in your new name, username, website, bio or private information, then tap Done or Save in the top right.