Isolating your online activity - Firefox Multi-Account Containers

Upon successful installation a notification appears on the top-right corner, and the Firefox Multi-Account Containers icon is added to your toolbar (Fig. 3). The first time you click the icon you are presented with a guide to better understand how the add-on works (Fig. 4).

Set up a container

You can create a container for any website, and assign a website to multiple containers. In this section, you'll learn how to set up a container for Twitter, but the steps are similar for other websites.
First, create the container by clicking the icon and then go to Manage containers > New container. Enter the name for your container and press OK (Fig. 5).

Now, navigate to the Twitter website, click on the toolbar icon, and then click Always Open This Site in... and select the container you just created (Fig. 6).

After you do so, Twitter links will open in its container, which you can check by the underlined tab and the symbol in the address bar (Fig. 7).

When you are browsing in another container and navigate to a Twitter link, you'll be automatically placed in the Twitter container. The first time this happens, you'll be asked if you want to open the link in the designated container (Fig. 8). To do so automatically from now on, tick the Remember my decision for this site box, and then click on Open in Twitter Container.

For more details on how to use Firefox Multi-Account Containers visit its official documentation.