Play the deal normally with 4 players and score according to the duplicate bridge scoring. After playing, look up the expected result (the result for the "closed table") for that deal in the Compensation Table.

Play several deals - the line, which gets more IMPs, wins.


Deal 1: You play 4H and it is just made. You are not vulnerable so you get 420 points. Your line (you and your partner) has 25 HCPs and a 9-card heart fit. The Compensation Table expects 390 points from you (25 HCPs, 9-card major, NV). You gain 420-390=+30, meaning 1 IMP for you.

Deal 2: You play 3D and go one down. You are not vulnerable so you lose 50 points. Your line has 19 HCPs, so the opponents' line must have 21 HCPs. The opponents also have a 8-card major fit and they are vulnerable. The Compensation Table expects 30 points from them (21 HCPs, 8-card major, V). They gain 50-30=+20, meaning 1 IMP for them.

Deal 3: Your opponents play 2S and it is just made. They are vulnerable and get 110 points. Both lines have 20 HCPs. In this case it is important who started bidding. Let's say that your partner was the dealer and started bidding. That means your line should score. Your line has only a 8-card minor fit and you are also vulnerable. The Compensation Table expects -40 points from you (20 HCPs, 8-card minor, V). You gain (-110)-(-40)=-70, meaning 2 IMPs for your opponents.

Deal 4: You play 7H and it is just made. You are vulnerable so you get 2210 points. Your line has 35 HCPs and a 11-card heart fit. The Compensation table expects 1610+2*150=1910 points from you (33+2 HCPs, 10+ card major, V). You gain 2210-1910=+300 so 7 IMPs for you.

Congratulations, you won a 4-board match with +1-1-2+7 = +5 IMPs.