I want to access files on my ubuntu server wireless. Is there a way I can do that?

I'm sorry if this is a stupid question, but I'm kind of new at this whole server thing.

Yes, of course. But what do wireless and a router have to do with anything? You haven't been specific enough as to what you want to do.

Yes you can. You just need to setup your wireless connection on your ubuntu server properly.

There are many methods of accessing files like ftp, ssh, scp , rsync and more. It always depends on your needs. In addition to that, if you want to share your files to a windows based clients you need to install "samba package". But if all your clients are linux/unix based, I would recommend you to use "NFS".

Installing SAMBA share:
Installing NFS
edit /etc/exports to configure nfs shares on your Ubuntu server.

Hope you find it helpful...

I want to be able to access files on the server through a wireless connection.

I'm guessing the wireless is through a router? and the server is connected to the router via wired ethernet? Then it's most likely the same as if it were wired, unless the wireless is blocked by a rule from accessing the rest of the network (other than to go out to The Internet ).
The post by ionrivera is a starter.

My experience in a nutshell:
I recently set up Samba from scratch, there are a few "gotchas" but it's not hard. My biggest problems was setting up permissions correctly, in my case I learned I had to use the forcegroup setting (Which forces the permissions of files written to the Samba share to belong to a particular group, so others can also read/write, if that's what you want. That, and the tutorial I initially read on it, I (Linux N00b that I am) assumed a group name they were using was a default group, but it wasn't; once I made my own group, and changed the permissions to that group, it's worked great since then.

If your ubuntu file server connects to your router either wirelessly or via ethernet cable, then it has the opportunity to share its files. Whether other computers can actually see those files will depend on a few things:

1)Do they understand a common file sharing protocol? Windows machines use Server Message Block (SMB) (and macs understand this protocol and can gain access to windows shares via wirless router). According to this article, "[Macs] can share files using Apple Filing Protocol (AFP), File Transfer Protocol (FTP) or Server Message Block (SMB) protocol." I'm not entirely sure what file sharing protocol linux machines might use natively, but you can in fact download and install SMB for debian/ubuntu as described by ionRivera.

2) Have you set up file sharing on the Ubuntu machines so that it is in fact sharing the files you want to share? This is partly an issue of installing the sharing protocol described in step 1 and partly an issue of configuring it. Just because you have the protocol installed doesn't mean your files are suddently visible. You typically have to specify what is to be shared by changing configurations. For example, in Windows you can right click something in File Manager and select "sharing..." and gain access to the share options. Macs have something similar. Ubuntu probably also has something similar.

3) Does a particular client have access to the shared items? Keep in mind that each computer on your network typically has a 'current user' (it may be Admin or Sneakyimp or Brewmaster619 or whatever) and that user has a username and a password. When something is shared (see step 2) you typically describe what users or groups may access the shared item. Some sharing protocols let you describe groups or just share things for everyone.

So YES you can share files on your ubuntu file server with out computers over wireless, but you'll need to figure some things out.