Mainer's suggestion would certainly work. However you would have to select the edited style from the Memories section as opposed to selecting it from the User Styles section. There are advantages to using Memories in that mic and harmonizer settings, Variation, Keyboard Mode, etc. is all stored in a Memory.
But to answer your direct question;
Once you have made your edits, press the Store button.
Then press the Right Arrow button above the Tempo/Data dial twice. This will select Style Preset. (see note below)
If you want new sound(s) to be active as soon as you select your style, press enter. What this will do is store this Style Preset in the first Style Preset location which is automatically activated upon selecting a style.
NOTE: Remember, there are a total of 8 Style Presets per style. If you want to save additional Style Presets within your style, press the Down Arrow button twice after selecting Store Style Preset, and use the Tempo/Data dial to choose one of the other Style Preset locations.
When you call up your style, press the Style Presets button to the left of the JAZZ Style Families button and you will have access to all of the stored Style Presets for that style.
Also notice that you can name Style Presets by highlighting the current name by using the Arrow buttons and then naming the sound using the keyboard and alphabet silk-screened below the keys.
I hope this helps.
Dave