Pokémon Sword and Shield comes with a variety of Pokémon that roam the wilderness with useful evolutions. While you can sometimes find those evolutions and skip the previous forms, you may want to raise one from level one to maximize its stats. A useful Pokémon to know how to evolve is Charjabug and transform it into a Vikavolt.
Before you can think about Charjabug's evolution, you need to find one. Its first evolution, Grubbin, can be found in the wilderness in the Watchtower Ruins, Dappled Grove and North Lake Miloch when it rains or during a thunderstorm. You have a fair chance of finding one in Wumberd Wumberd and Route 1 during the first part of the game, but it's low-level, which might work great for aspiring coaches early in the game. You can find Charjabug in Axew's Eye when it rains, and in Dusty Bowl and Hammerlock Hills during a thunderstorm.
Now, when you have a Charjabug, you are ready to work towards acquiring a Vikavolt. To turn it into one, you need to give it a milestone. You can find a storm in all Sword and Shield. Some of the notable places include talking to the Digging Duo in the Wild Area to have them potentially dig one for 500 Watts.
You can also find one in the North Lake Miloch region in the wilderness area. It is the Poké Ball found at the top of the hill east of the bridge. Climb on it and look for a small cliff that looks towards the large tower in the distance.
When ready, give your Charjabug the Thunder, and you should see it evolve into a Vikavolt in no time.