Choose 4 digits in the "Decimal Pricing" option under the "Trading Tools" section.
I don't know how valid the informations are, 4-digit pricing has become rather rare. Saxo Bank is one I know that still has a 4-digit pricing system.
Why are you looking for a 4-digit broker? 5-digit brokers have better spreads. It's easier for a broker to reduce the spread from let's say 2.0 to 1.7 then from 2.0 to 1.0.
I just want to use 4 digit brokers for analyzing the market .I have a problem with metatrader with 5 digit brokers .It stop working when I want to analyse the chart and draw some lines for about 4-8 seconds every time .I don't know what's wrong with that But I do know it's working fine with 4 digits brokers.