I do step climbs by entering the the height increase in the FMC. Its on the page where you set the ZFW, ALT and CI. I usually put 2000 where you see the word ICAO. The FMC then figures out when to do a step climb.

I also set the first step just above the optimum height shown on the VNAV page. E.G. If VNAV says that the optimum altitude is FL304 i set it to FL310.

Then the FMC will figure out how long/far before the next Step Climb.

Hope i make enough sense for you to understand what needs to be done. Jack S. might be able to better explain it though because he seems to be better informed than me.

Mark