I think a direct transfer from MyRoute-app from your mobile phone to your TomTom is not possible. Therefore you have to do 2 steps.

Save your route as *itn and/or *.gpx 1.1 format file on your mobile phone. This file will be stored in the download folder on your mobile.

Copy this file from the download folder to your TonTom satnav. This should then recognized from your TomTom. I don’t own a TomTom therefore I can’t give you more advices.
If not already installed you can find a filemanager for this task for free in the google playstore.