After you shock your swimming pool it will take 24 hours for the pool water to clear up after shocking it.
When you shock the pool water you need to turn on your pool pump and allow the pool pump to filter and circulate the water for 24 hours.
Wait up to 24 hours before going swimming in the swimming pool after you shock the pool water.
If you don't notice the pool water clearing up enough after 24 hours then you may need to run the pool pump another few hours to another 24 hours and the pool water should clear up.
As long as you chlorinate the pool and shock the pool often enough and use the pool pump to circulate the pool water you should not need to drain the swimming pool or change the swimming pool water until the next season.