From my son:
Go to the ea fifa website and go into the web apps. Sign in with your ea account and click on creation centre. Go to the teams section and search for "dumbarton". Then bookmark the team by clicking on the team and then the bookmark team button. Next time you sign in on your console go to customize fifa, then chose creation centre. Just select the team from the menu and it will start downloading. Be sure to turn the match day squad updates off in the team selection and scroll to the creation centre section. From there simply select the team and play! I think you can use them in career and tournaments but I'm not sure how.
it is a bit involved.