This guide will let you know how to catch Eevee in Pokemon Legends Arceus.
In the first map, you will need to head over to the horseshoe planes while you explore. You can put your markup in the middle of the title and wander over to that area.
This Pokemon is a rare spawn, so you will not see it every time you go there, but you have to head over to the general vicinity and look around in the grass or the general area. When you spot it, you have to go closer to it, but be careful because Eevee does tend to run away. So you must crouch and get in the grass so that the Pokemon will not see you coming, and you also have to be a little bit more stealthy.
If you don’t find this Pokemon, you have to fast travel back to the base camp. You can then go to interrupt the bed, select a different time of day, and then upon respawning, you can then go back to that location and search again. It is a rare spawn, so sometimes you will not find it, and you might search many times back to back but keep trying, and you’ll find its spawn.