Scrivener is not designed for multiple writers to work on the same project at the same time. You’ll need to develop a process for coordinating access.
For example, if you each will be working on different documents, then one of you (A) can work in the master version of the project, while the other (B) works in a copy of the project. When (B) is done making their changes in the copy, one of you can integrate the changed docs into the master version.
That’s just one idea. Search the forum for “collaboration” for other ideas. This topic has been discussed many times (here for example).
Best,
Jim