If you want to do it manually......here's one way to do it. A standard modem/router will do the job but it depends exactly on what you want the server and all the connecting computers to do, and how many computers you need to connect.
I would still continue to use ONE wired computer as the main setup machine. You might want to use the server as the primary machine but that's up to you. Create an administrator login on that machine, with a password, and connect through ethernet to the router. On the primary computer, create a "Workgroup" name that all the computers will join up with. Next, in the router settings, be sure to change the settings so that ONLY wired connections are able to make changes to the settings. This helps prevent wireless computers from changing your setup in the router.
Now access ALL the other computers and create new login profiles with EXACTLY the same administrator login and passwords as the original one you created on the primary machine. Login to each computer using that same admin account, join up to the workgroup you created earlier, and allow each wireless machine to connect to the internet.
Once all the machines are connected to the workgroup and the internet, you can go about sharing any files, folders, and printers on the server or elsewhere.
Hope this helps.
Grif