Use the UCX as your TFTP server. Using WINSCP login to the UCX. Navigate to the TFTPBOOT folder and load your files there. You can load all .cfg files as well as firmware, jpegs for wallpaper, contact files etc.
There are multiple ways from this point to point the phones at the UCx to retrieve config files.
If DHCP server can provide Option 66, you can have the DHCP server supply the Provisioning servier IP address along with the LAN IP address.
If no option 66, plug all your Yealink Phones into the network. After they have received IP addresses, go to Batch Configuration in the UCx and Click on magnifying glass to scan the network. It will find all the Yealink phones and present you with a list including a link to each phones IP address. Click on the IP address of a phone and it will bring you to the phones GUI. From there go to Settings/AutoProvision and at the TFTP server setting enter TFTP://xxx.xxx.xxx.xxx where xxx is the IP address of the UCX. Click confirm and then click on Auto Provision.
If you have your config files in order the phone will register itself and you will see it appear in Reports/Extension Overview.
If you take the time to learn how the Common and Mac .cfg files work it will be a breeze to deploy these phones. If you can get the IT Vendor to enable Opt 66 on the DHCP server you will not have to do anything but plug the phone in. The config files will do the rest.
Note, Each Model phone has it's own Common .cfg file example: T23G uses something like y0000000044.cfg and the T29G will use something like y0000000043.
You can find out the type of Common.cfg file the phone is looking for by turning on Packet Capture, Do a Auto Provision on a Yealink phone through the Gui and then review the Packet Capture in Wireshark. It will tell the name of the file that particular model of phone is looking for.
Or, you or Weston can give me a call sometime and I will send you some information that will get you started.