There is no direct flight from Yichang to Xian or Guilin. You may take bus to Wuhan, which takes around 5 hours, and take a flight. Alternatively, you may take a train from Yichang to Xian, but no direct train available to Guilin.

Yichang Airport is very limited on flight schedules except to Shanghai, Chonqing etc.
Regarding the Yichang-Guilin leg, there is a long & slow(14 hour) train route to Liuzhou which is a 2 hour bus ride to Guilin.
This train has bad toilets and is unsuitable for foreigners unless you can get a sleeping berth. These need to be booked beforehand.