Time Tracking by Customer

I have created a column called Customers. I have Time Tracking enabled. We provide managed services and I want to track the amount of time that we have spent on managed services tickets for a customer. I do not see a column type for my Customers columns in settings under the Time Tracking widget. I also only see People in the quick filters. I am trying to get the total amount of time spent for a particular customer for the month and the year. Can someone point me in the right way to get this done.