Ive only just started running, as like you i want to do a race and get sponsorship.
I downloaded an app called walk jog run, and chose a training plan from there. (there are lots to choose from)
From someone who three weeks ago couldnt run to the end of the drive.. tonight i ran over 3k.. which is a bit of a miracle for me, im 46 and carry a few extra lbs!!! good luck with what you are doing,,