Generally, when you open Instagram posts and try to delete a post, the delete option is not available in the menu list.
However, here are the steps to delete the Instagram post on your computer:
Step 1 : Launch the Chrome browser on your desktop.
Step 2 : Open your Instagram profile .
Step 3 : Right-click for more options and select Inspect . This will open the Chrome browser developer console.
Step 4 : Click the Switch Device toolbar in the Developer Console.
Step 5 : In the drop-down menu, select any device like iPhone X and set the scale to 100% .
Step 6: Reload your Instagram profile page.
Step 7 : Click the Flows icon to switch.
Step 8 : Click 
for more options
Step 9 : Select the Delete option .
Step 10 : Finally, click the Delete command to confirm that you want to remove the Instagram post.
That’s it. Your Instagram post will be deleted from the desktop site on your computer. As mentioned, you will be able to delete any browser post without using any external software.