There are several apps that you can install to do it, but recently there have been major concerns about the apps accessing your accounts. Especially on YouTube where they have been using your account to generate views that appear genuine. They then sell the views to their customers.

 

The good news is that you don't need any other software besides one of the standard browsers. Here's how to easily switch your browser's mode to make Instagram think you are using a mobile browser. Instagram then display the upload and editing controls that let you post your photos to all your friends.