Training schedule and workouts for trying to go from 23mph average to 25mph by spring

Hey so I am new to Road Cycling (previously a mountain biker). I got my first road bike (Domane ALR 4 Disc). I did a 10 mile time trial solo and it took 27 minutes (~23mph). It was calm wind and mainly flat with some long but not steep hills (1-2 degrees). I think that’s a good starting time but I...