How do I set up the back-end/server for an MS Access multi-user app

Take a look at Setting Up an MS Access Database

You don't need a server per say, just a shared folder.  If you have a server then great, otherwise you can share it off another PC.
Never use Access over a wireless network, always a wired LAN.
For multi-user use, splitting the db is critical.  Each user must be given their own copy of the FE, never share a common copy between users!

as others mentioned just grab a machine with at least 4 gb of memory..the Os is not that important.. even Windows XP can serve the purpose or even a Linux distro with Samba..just make sure you have a steady Lan ....with Gigabit connection for all the machines ... pay attention to steady...ping should always be below 1 ms without strange spikes.. personally i would go with a refurbished server with at least 2 hdds in raid 1 and thats about it

Thank you all for the helpful comments. They cleared up quite a bit of confusion. Now, I am asking for additional help in the following areas:

• Can you refer me to the procedure for setting up a wired LAN that includes the FE & BE computers?
• Is the LAN necessary for me to link to the BE on the other computer
• Or, can I just create a shared folder on the BE's computer, and link to it from the FE?

Can you refer me to the procedure for setting up a wired LAN that includes the FE & BE computers?

  I think your possibly confusing something here; a "LAN" is a Local Area Network and it connects computer together.  Each computer needs a NIC (Network Interface Card), and you need a switch, hub, or router, plus some cable.   It is not something that is special for hooking up an Access database.

  What exactly is the situation?  If your in any kind of office and you already have internet connectivity, and/or your file and print sharing, then a "LAN" is already in place.

Is the LAN necessary for me to link to the BE on the other computer

  Yes.   They cannot communicate with one another otherwise.

Or, can I just create a shared folder on the BE's computer, and link to it from the FE?

 That's ultimately what you'll do with a LAN in place.

Jim.

Most business networks are LAN's where all the computers are networked using wire and connected to one or more servers which host files, your email, and your SQL Server databases.  You can use a peer-to-peer network which is what you get when you set up a network at home.  In a peer-to-peer network, all connected PC's are equal (there are no servers) and one or more of the PCs share folders that other PC's can see.  You would just put the BE in a shared folder.

Most of the time, the Access BE is stored on a standard file server where other shared files are stored.   Create a separate folder for the BE so you can use security to keep unauthorized users from accessing it.  

As others have mentioned, it is a recipe for disaster to use an Access BE on a wireless network.  Access cannot recover from "blips" and you are very likely to loose data or end up with corruption if the network is unstable or slow.

After setting up the shared folder on the "server", do I need to map the folder (or the server), to a new drive letter on the client computers?

Yes, or you can refer to them with UNC naming:

<servername>\\<shareName>

 So if your server was "accounting" and the share name was "BEDB" then:

  accounting\\BEDB

 I myself generally map a drive letter though.  Less to type<g>.

Jim.

I noticed that, when I designate a folder as 'shared', it asks me to "choose people to share with". Does this mean I  have to identify the user name on each of the client computers?

Thank you all for educating me on LANs. Now to implement it in the workplace!