While doing some runs inside will get your ready, you will want to practice running outside to acclimate your footing as well as your bones, connective tissue, joints and muscles to running on a road surface. You may want to check with your local running specialty store to see if they offer social runs or a half-marathon class. If not, you may want to visit the following website rrca.org
to see if there is a running club in your neck of the woods.
RUN SPARK HAPPY!