Welcome to the Running forum! Congrats on finishing the C25K! That is how I started as well. If you liked the program and it worked for you, I know they have a Couch to 10k program. You could just continue on with your training to reach the distance. I didn't specifically train for the 10k distance. Once I completed C25K, I started on a marathon training program. Since you still have 4 months till your event, I would suggest keeping up with your 5k distance at least a couple times a week and then do a longer run on the weekend. Add distance slowly with maybe a 1/2 mile increase each long run. If you felt really fatigued on a long run, step it back the next time or retry the distance the next week. It is really important to get a good base (like the 5k distance). Once you feel comfortable doing 5k, it really isn't too tough to add distance. I have heard more than once that it is tougher to go from nothing to 5k, than it is to go from 5k to 10k,half marathon or even marathon. It really is true!