My experience is with Android but Apple can't be that different.
Download RUPI Manager App, free on Android and probably free on the IStore. I have found the best way is to take in my POI data in the TomTom ov2 format. Place this file in the Import folder in RupiManager and then export it out of RupiManager in rupi format. The exported file will have a .exp.rupi extension now. Just rename the file deleting the .exp part of the name and leave the .rupi. Place that file in the Sygic/Maps/Import folder together with the .bmp icon which has the same name and the next time you run Sygic it will ask to you want the new dataset imported. RupiManager has never let me down, it just works every single time perfectly. It is the icons that I have inconsistency with.
Hope you get sorted.