Hi- the gobo rotator is built in to the E-910FC fixture, you don't have to add it separately. You can add a gobo to a frame list and apply it to the Gobo Rotator field in the properties editor. In the properties list for your fixture, double-click on the space next to Gobo Rotator. Capture will ask you if you want to create a copy of the framelist for editing- click YES and the framelist dialog will open. You can then drag and drop a gobo into the framelist. That gobo rotator will respond to the gobo rotator channel that is built into the fixture profile.
Hope that is helpful!