Set up common database server for vb.net application
First you'll need to nominate a computer that's going to act as the database server (obviously this will need to be one that all machines running the application can connect to over the LAN and that is always going to be running when the application is in use). We'll call this machine "server"

On "server" download and install SQL Server Express from here: https://www.microsoft.com/en-us/download/details.aspx?id=42299 - you'll want the version that is called "ExpressAndTools" and make sure you get the appropriate 32/64bit version depending on your hardware and OS (installing with default settings should work well enough for your purposes). 

Next you'll also need to download and install SQL Server Management Studio on the computer that currently has the application/database on (it's from the same link as above and is just called "MgmtStudio"). Once that's installed open it up and should pop a dialog asking for details of where to conenct. Enter "(localDB)\V11.0" as the Server name, select "Windows Authentication" and click on "Connect". You should then see an entry in the left hand column called something like "(localDB)\V11.0 (SQL Server V11.0 - domain\username)", expand that entry out and you should see a folder called "Databases", expand that and you should see an entry matching the name of your application's database. Right-click on that Select Tasks -> Backup. In the backup dialog make sure it's set to Backup type: FULL with the destination being "Disk" and click on "Add" to chose a folder/filename for the back up and then click Ok to start the backup.

Once that's completed you'll need to copy the back up file to the "Server" computer, then open Management Studio on there and when it asks you for connection details use "localhost\sqlexpress" with Windows Authentication. Once your connected expand the node labelled "localhost\sqlexpress" in the left hand column, right-click on "Databases" and select "Restore Database", in the resulting dialog change the "source" radio button to "Device", click on "..." and then click on "Add" and browse to the backup file from earlier. Once that's selected it should populate the rest of the restore fields for you and you can just click "Ok".

Once that's finished you'll need to update the "App.config" (or "Web.config" if it's an ASP.NET application) to reflect the new database connection string. You should be able to find a line similar to thi:

&lt;add name="DefaultConnection" connectionString="Data Source=(LocalDb)\v11.0;AttachDbFilename=|DataDirectory|\aspnet-WebApplication3-20161207104129.mdf;Initial Catalog=aspnet-WebApplication3-20161207104129;Integrated Security=True" providerName="System.Data.SqlClient" /&gt;


change that to point to the SQL Express server so it's something like this (obviously fill out your actual details!):

&lt;add name="DefaultConnection" connectionString="Data Source=nameofserverhere\sqlexpress;Initial Catalog=nameofdatabasehere;Integrated Security=True" providerName="System.Data.SqlClient" /&gt;


This should then mean that when the application looks for it's database it will look to the one on the "server" not try and attach the mdf file.

It's been a while since I did this to be honest so hopefully I haven't missed any steps!