A lot of these are already added in the default "distractions" list provided with Cold Turkey. If you deleted this default block list, there's an easy way to get it back:
Once the interface is open, go to the "Lists" tab, and create a new block list. First, give it a name and in the website tab, click "List" then hover over "Import List >" and then click "Distractions."
Nice! Now you have a nice big list of distracting sites to get you started. Make sure to go through them all, and then click "Save." You can now start a timer or schedule the block for the block list to be active.
If you want to delete an entry from the block list, just select it and hit the delete key on your keyboard.