This is a pretty easy achievement to get. If you discover Rygjafylke further you will find the first 10 quickly. (check your map legend
for the World Event icon)
In the village of Stavanger (bottom left corner of Rygjafylke) there are already 3 to be found and just around it also 2
As soon as you start a World Event you will not get a new marker, so listen carefully to the character says. Sometimes you just have to follow them, find an object or make kills / show skills. If you lose character, you can always return later and start the conversation again.