When creating a homebrew campaign it is important to fully immerse the players.
One way to do this is by creating a primer. Make sure you carefully detail the pantheon and mythology. It is also a good idea to included a map with all the major geography. The full history of the world is important - include a timeline with all major events, and give it to players to read before the game starts so they are fully prepared.
Another way to do this is to just explain the campaign concept at the start of session 0, start at the creation of the world and walk the characters through the entire history so they are up to speed. Don't allow them to look at their phones while you do this. It is important to have their full attention throughout.
It is aslo important to put a fresh spin on all the tired generic races. Do something truly original - if in your wor;d Dwarves are mastodon riding aesthetes who live in the deep desert and are known for their colourful dances and song while elves are short lived gadlies who are known for their stoicism and grim demeanour as they live under the thumb of the cruel and tyrannouos halfling empire than your game will be truly memorable.
You CANNOT begin character creation until the players have fully grasped the nuances of the campaign setting.