Sure ... it's fairly simple, but it's also complicated in the sense that you'll have to create a modified version of your site's skin.
To prepare for this, I'd recommend that you review the many tutorials here that deal with skin construction, and with Lee's "Skinning Toolkit."
But ... you want to step into the shallow end of the pool first, and not the deep end. I'd recommend that you start with the tutorials that deal with the
Red Leaf Skin.
And, if you are a relative newcomer to DotNetNuke, I'd recommend that you start with some of the tutorials for beginners that you'll find
here.