Creating a clickable phone number in tagline

I’ve never even posted in a forum before, so, this is all new. I built the site about a year and a half ago. I’ve learned a little here and there, but I am finally stumped. I need to have my phone number clickable in my tagline so that mobile users can call from my website. Unfortunately, I have no idea how to do that. I’ve seen other posts about it and that I need to add a snippet into the filter? I’ve even looked up how to find the filter and alter it.

I’m LOST! Please help? I need idiot directions! Haha!