Just:
- store the access file in a network share
- modify the connection string to point to the file in the network (possibly use UNC)
And off you go. The program (excluding the connection string) remains the same.
For the connection string, see:
http://www.connectionstrings.com/access[
^] /Network location)
Now, this isn't going to be a client server program. It still is a program using a single shared file. If you really want to convert this to client server then I suggest that you move on to Sql Server instead of Access. You can download an Express edition for free:
http://www.microsoft.com/sqlserver/en/us/editions/express.aspx[
^]