Did you install SQL Express 2014 or did you choose the localdb version during the install?
Either way if you use multi terminal you need to install SQL Express 2014. Here is a tutorial to get you started.
Here is a great companion tutorial to help you if you have issues.
Here is a general database setup tutorial it explains the connection string. The menu might be slightly improved in v5 but the concepts are the same.
This won’t help you with setting up multiple terminals because you must use SQL Express for that however the connection string for a localdb install looks like this:
Data Source=(localdb)\MSSQLLocalDB; Database=Sambapos5