Take it slowly, build up by degrees. If you push too hard all at once, you risk injury. Slow and steady. I've gone from 2 miles to 30 mile rides, needed a bike fit to get comfortable enough to do it. My butt on my Brooks saddle still talks to me around the 30 mile mark, so it might be a while before I go further. Just focus on enjoying the ride as you go, not on the #. You'll get there before you know it!