A job can be edited in the Web Portal and the App (depending on the user's permissions).

Web Portal, Jobs > View Jobs > Edit > make changes > save / dispatch.

To edit a job in the scheduler, click the job that you would like to edit > edit > make changes and save / dispatch. 

To edit a Job in the App you will need to go to Jobs > search the job you would like to edit > swipe left > select the edit options and make your changes > save / dispatch.

Through the Diary on the App a job can be edited. Diary > press on job that you would like to edit > select edit > make changes > save.

Or holding down on a job in the Diary will take you to the job page as shown above and the option to edit is available.