Both destinations are served by Amausi (LKO). Since there's no flight route between them, the best way to travel is by road.
Lucknow
Fly to Amausi (LKO), then travel by road to Lucknow. Taxis, buses, and private cabs are available from the airport.
Sitapur
Fly to Lucknow (LKO), then travel by road to Sitapur. Local transport options include taxis, auto-rickshaws, and state buses.