Next step is adding content.
The most important thing to tell you is that everything is easy to do. It's a matter of download, unrar, copy and paste. So no worries.
The next important thing is to do it slowly, one step at a time. This I say because your device is rather limp. When you overdo it and want too much in a short time, the chance of failure is big. But do it slowly and discover how far you can go and you will have a travel compagnon.
When your language is already filled in (iGO is in your language as is the voice), you can skip adding new ones. I do not know that iGO download I recommended very well, but if there are languages and voice files present you don't need at all, you can safely delete them. It will save up memory. Keep the ones in your language.
You cannot use TTS (voices that announce street names) for sure, so do not bother downloading them.
Maps you will find here :
http://www.navitotal.com/forumdisplay.php?82-Maps-buildings-dem-POIDownload what you need. Also: Since your device has lack of processor power, stick to what you need! No building or DEM file. No eye candy, your processor can't cope.
Add 1 map at a time in the map folder (
http://www.navitotal.com/showthread.php?11326-where-to-put-map-related-files-in-iGO-Primo) and test if it works. Then another map when you need it. The same with POI files.
By 'test if it works' I recommend a few routes in simulation. A short route will test if it works at all, a long route will test the memory (or lack of) of your device. When possible, take your device on the road. Driving a route in real life will show weaknesses (like announcing a street to take when you have passed it already).
When you want to read something about installing iGO:
http://www.navitotal.com/forumdisplay.php?128-How-to%E2%80%A6