Hi Neelam.. you can try Bla Bla Car.. It is a good platform for carpooling. not sure how popular it is in Edinburgh, but it works really well here in India.
There is a train between Edinburg and Fort William which starts from Edinburg and runs on all days. It is an overnight train. Another fast way is driving which is 3 hours drive. There are no direct buses for you need to travel to Buchanan and board a bus.