When there is a step in the crank I try a couple of approaches. You can directly wrap a couple of turns of electrical tape so they just cover the step. Grease up the seal/tape and carefully work the seal over the step. It should slide over without hanging up or potentially scraping the lip. Another method that seems to work is using a 1/2" sleeve of copper water pipe. Chamfer the ends of the pipe, work the greased seal onto one end, slide the pipe over the crank and up flush to the step. It should transition nicely and slide right over without rolling the lip. A large fender washer over the seal can help keep them flush when tapping them into place with a socket or such.