How do I ask or let my boss know I'm interested in adding more to my work load?

I’m part of a small digital marketing team at one of the top car dealerships in my city. I personally handle the photos department, but I noticed on the social media pages there are a lot of grammatical errors :X

I want to express to my boss that I’m highly interested in adding copy editing to my work load. It shouldn’t take more than 15 minutes to go over the text being applied to the social media that day.

The thing is I’m kind of embarrassed and the old dog of a journalist in me really wants to edit the hell out that crap! I’m burning for this!