If you look in the Documentation folder of the archive, the Hnefatafl.pdf document contains some details of what can be done, like page 15 and 16 the description of the “Blood Eagle” and “Berzerker” moves where you can capture two or three opponents at the same time, and page 18 the various conditions on which the King can be captured.
The game of Hnefatafl is relatively well documented, you can search on youtube for “Fetlar Hnefatafl” for plenty of small tutorial videos, just remember that there’s one specific rule which is different, in this Oric version of the game it is allowed to move a piece so it stops between two opponents without being taken.