There are several publications giving advice on how to get your aircraft properly trimmed. Some of these are shown below.
The GBRCAA trim chart should be your first choice when initially trimming your aeroplane, however the other articles will be interesting & contain lots of useful information.
Trimming, to fine tune your aircraft, should ideally be done on a fairly calm day. It takes lots of practice to get the model well trimmed & even when you are happy with the trim, it will need to be re-checked on a regular basis & probably readjusted slightly, many more times.