This article explains how to unlink your Instagram account from Facebook using a computer.
Steps
Step 1. Visit https://www.facebook.com using a browser
You can use any browser, such as Chrome or Safari, to log into Facebook.
If you are not already logged in, enter the data required to access Facebook
Step 2. Click on the down arrow
It is located on the blue bar in the upper right corner of the screen. A menu will appear.
Step 3. Select Settings
Step 4. Click on Apps and Websites
This option is located in the column on the left side of the screen.
Step 5. Hover your mouse cursor over the Instagram icon
If you don't see it, click on Show all to view other applications. Two buttons will appear to the right of the application name.
Step 6. Click on the X
A pop-up will appear to confirm the operation.
Step 7. Click Remove
The Instagram application will no longer be linked to your Facebook account.