It is recommended to set up an automatic job to fetch new posts. Automatic job periodically executes a script which fetches new social media posts. However even if you don't set up an automatic job, a plugin will still work. Just specify the value in "Update every (minutes)" field. Then basically with every request to get feed data, a plugin checks if it's time to update the feed. Updating can take up to 5 seconds so the user will need to wait. In order to avoid it you need to use an automated job.

When you installed this package, a new job named "Update Social Feed Data" was created. You can find it System & Settings -> Optimization -> Automated Jobs or by going to this link in your website /index.php/dashboard/system/optimization/jobs. 

You will see a new job added and clicking on the "clock" icon, will open a modal with a few options.

The first option is easier to set up but the second one is recommended. If you run your website on private server with SSH access on Ubuntu, you can follow this tutorial how to set it up https://help.ubuntu.com/community/CronHowto. If you are using shared hosting, cron jobs should be in your control panel.

I recommend to set it run every 2-3 minutes as it's designed to update 1 block at a time (always update the oldest block) so you will not exceed API calls limit and update the blocks quite frequently.