Thank you for your post.
A runtime solution cannot be used over a network, so if you want two users to share a file, you need clients to use either FileMaker Pro or FileMaker Pro Advanced.
If you are unable to create data files, then your permissions may be set to Read Only. Change this to Read/Write, and you should then be able to create files. Performing a quick search with a browser search engine gave me:
Let me know if you continue to run into problems.