Randomly associated A, B, C, and D with the four edges of the board. Each one can be on either the 1 side or the 2 side, any mixture is permitted. The provided randomization cards are a fine way to do this.
Exactly. The rules describe how the cards can be used to do this. Simply randomize them face down (including some random rotations of individual cards) and place them at the four sides of the board. Then turn them face up. Whichever number (1 or 2) contacts the edge of the board, use that side of the track for that company.