time machine backup over wifi with el capitan

I'm attempting to set up Time Machine backups for both my iMac and my macbook pro. Both machines are older and running El Capitan. I have Time Machine successfully going on my iMac and have read on the Apple help pages how to make a folder on my iMac a Time Machine destination for other computers on my network. I've gone through the instructions of making the folder shared and I can access it from my other computer. However, I keep seeing an instruction to select "Advanced Options" when I control-click on the name of the folder in the shared settings menu, but I do not have an "Advanced Options" option available to me. There's no where that I can see to actually make this a Time Machine destination. Is this even available on this OS? Has anyone else been able to set up a Time Machine backup over wifi?