Everyone talks / rave about the ROTF Jetpower Prime (aka combined version of both Leader Class Optimus Prime and Jetfire). Rarely, one reviews the Classic version.
In the classic version, the Jetfire is not exactly combined / connected to Prime unlike its ROTF counterpart. It's just rested on Prime and the only way to so-called locked Jetfire onto Prime is to adjust both Jetfire's limbs and Prime's windscreen to be as close as possible to one another.
For the full step-by-step instructions / review, please check out this Youtube video by misfitrobot.