Right near the beginning of Valhalla, shortly after you’ve established your own Settlement in England, you can undertake Raids into enemy territory. Simply approach the symbol for Raids on the map, represented by two red axes, and use the horn on your item wheel to summon your Viking longship. Hop on board, and approach the Raid location to kickstart the combat gauntlet. Because Raids are filled with enemy forces, there’s an increased chance to gain Silver from their corpses, as well as from any containers scattered around the local vicinity.
You can also acquire Silver by using your raven. Pressing up on the d-pad or the corresponding key on PC, you gain a literal birds-eye view of your nearby surroundings, honing in on points of interest within the nearest few hundred meters. What you need to be on the lookout for are gold glowing symbols which denote nearby points of Wealth.
Each territory in Valhalla has a set amount of Wealth to be uncovered. You can view a territory’s wealth by pausing the game and viewing the world map. By hovering over territory with your cursor, you can see how many instances of Wealth there are for Eivor to uncover. The quickest way to find points of Wealth on the map is to use your raven to pinpoint them.