Just keep riding...
minimum 3-4 times a week...
have at least 1 rest day a week
ride some of your rides at recovery pace (slower than you need to)
do some interval training (like short sprints inside a training ride)
if the course you are aiming to ride is hilly, do some hill reps once a week

Keep riding... for the distance and the terrain your goal ride is...

Keep on.... riding

Oh, and have fun doing it... thats the most important bit...

Look forward to hearing more about your rides