I am new to XenForo and web development and a great way to start would be to provide assistance to the current developers by testing their addons/styles and any resource.
I just want to add a little bit of an appraisal to this.
MOZ has been very kindly helping me with my Notifications add-on (see below). He has been a fantastic help in collating all of the suggestions people have been making for improvements to my add-on and he's on my go to list if I ever need any testing work done in the future.