The sign for "trade," "replace" (or even "atonement") is done by using "F"-handshapes on each hand. Hold one hand forward and one hand near your body. Then switch the positions of your hands.
TRADE:
If you mean "trade" as in "trade in," "exchange," or "swap" then use this version of the sign. It is done very quickly. The hands are in "closed-X" handshapes. Hold one hand in front of the other. Switch places and then switch places again but do it in one smooth motion (no stopping until the end of the sign). When you do stop, do it forcefully.
EXCHANGE / swap:
Animation: TRADE (version 2 "exchange")
Also see: EXCHANGE
Also see: CHANGE
Notes: