elder is in forest, go around the mountains and swamp

meadows -> eikthyr
forest -> elder
swamp (and farm some obsidian and frost glands in mountains for better arrows) -> bonemass
mountains -> moder
plains -> Yagluth

fine bow and fire arrows are good for killing elder
walk to avoid his attacks and traps
bash skellies/grays with mace and keep firing arrows at elder
bring along about 2-3 stacks of fire arrows, shouldnt need an extra bow but bring one if you want

when you start/join put in the map seed to see the boss spawn locations
https://valheim-map.world/