WSUS not finding Computers on Network.

After installing WSUS on  a server there was an issue of getting the computers on the network to join themselves to the service. We tried connecting manually to the pc's through the WSUS interface off of the server, to no avail. Tried logging into the pc's with an account with administrator rights and then tried connecting to them again. Nothing. We have found out that with new computers or with pc's that have never been updated we had to first go to the Windows update website, then manually run the installer on the pc. There are some requirements that the computers have to meet in order to use the update service. After installing anything required to get the updates the pc's began populating within the WSUS program off of the server.