After you've finished shooting, import your footage into your editing software. For this how-to we're using Adobe Premiere Pro, so the exact sequence of steps might vary if you're using a different program.
Once you've finished editing, you'll want to set the workspace to color correction. You can do that by pressing Shift-f12 or by selecting Window >> Workspace >> Color Correction.
Drag the Three-Way Color Corrector selection from the Video Effects >> Color Correction menu onto the clip you'd like to correct.
Go to the Effects control for the clip you're working on, expand the Three-Way Color Corrector selection, and check Show Split View.
If you used white, gray, and black balance cards on set, it will be easy to balance your footage. Move the footage to a point where you can see the balance cards.
Select the black balance eye dropper and click the black balance card in the frame. Repeat for the gray and white cards.