Start with GIT: it's built in to VS these days:
The Git experience in Visual Studio | Microsoft Docs[
^] so all you'd need is a repository (GitHub is out there though so you may not need to set up your own server).
It's a version control system, which lets everyone work with the same project code - which probably isn't exactly what you are after, but adding a "utilities project" could be a start towards that.
Including that project in your main project would give you access to all the utilities (and the chance to add new ones).
I think you probably need to discuss exactly what you need with the rest of the team though before you start going ahead - and we have no real idea exactly what you want to do, or where you want to get to. Or where you are at the moment, for that matter!