I had a Celestron mount and I connected it via a USB cable from the hand controller to the RPi. On the RPi end of the cable it was the USB A connector and I think on the Celestron hand controller side it was a mini USB connector. I don't know what model Celestron mount you have but using the hand controller as the connection seems to be the predominant path. If you provided more information about the mount model perhaps we could be of more help.
G'Day Frederick thanks for replying I was starting to wondering if I was the only person that had a problem . I have a Celestron Evaluation 6" and I am trying to connect Kstars (I have the right cable from what you described) ,The problem is I can see the Celestron marker on Kstars map but when I move the mount in Kstars it will not move ,when I look at the Indi control panel it is saying it's connected but the the green lights on the left hand side mount info page are not lit up like the rest setup pages are. I hope you can help
If none of that is of use, depending on what kind of computer you're connecting to it is sometimes necessary to download a USB to serial driver. I had to do this when I was using a Mac a few years ago.
Finally, I noticed in the link I shared above that it is possible to connect that mount without using a cable. Depending on WiFi signal and how far your computer is from the mount this can sometimes lead to communications challenges of course.