I did something similar for my map. I don't have gplates installed anymore so I can't give details because I don't remember. The basic idea is to create a plate using one of the drawing tools, don't remember which. Then set the Euler pole for that plate and move it to where you want. In the settings for each plate there is a bunch of data, somewhere in there you add plate movements by changing the start and end time. I don't know if this helps I really don't remember the interface at all. Check out the gplates user manual, your going to be playing with plate reconstructions menue a lot, it gets tedious.