I second the Jeff Galloway recommendation from
@Ariel484 . Jeff Galloway's plans do not feel impossible, but rather doable. I've ran all but one race using his plans, and the race where I didn't follow his plan worked because I understood how training plans work and knew how to build mileage up quickly, yet safely in a very short period of time.
These boards are also a wealth of information and very encouraging runners. Most importantly, the most successful of the runners on here are very encouraging and more than willing to help those of us who still have much to learn.
Before my first race, I was very nervous about not finishing. Consequently, I basically didn't talk to anyone about how my training progressed. This left me feeling very unprepared and terrified I would not finish despite having put all the long runs in. Because of this, on race day, I started off way too fast and very nearly became a self fulfilling prophecy since I was running much faster than I had trained for and had severe shin pain. I realized I could not go much further in that kind of pain, so I decided I would either finish the race by walking it or get taken off the course because I was too slow. But I would not quit. 3 hours later I finished. Technically, this is still my fastest half marathon, but it also remains the only race in which I did not stop for any pictures whatsoever.
What did this teach me? Trust
your training. Run
your race. If you put in the training, you will be successful.
Don't be afraid to ask questions on these boards. Someone will answer and you will learn a lot.