How to apply custom taxonomy to multiple posts

I want to assign a new taxonomy to over 100 existing posts and I can’t get it to appear as an option on the posts listing screen. I also clicked the “screen options” expecting to see my new taxonomy as option in there so I can select it and make it a new column but it isn’t there.

If there is no way to get the new taxonomy to appear on the posts listing screen, is there any other way to assign the taxonomy to multiple posts without having to go in manually to every single post? #ballache

Here’s an annotated screenshot of the back to explain what I’m on about!