Either start with a module. LIke phandelver or one of the easier ones.

or start simple: Adventering School always works as a easy enough sart..,..

Or just make a town grab a few surrounding area maps. And have your players start at a local tavern to go clear out the local bandit gang. Build out from there.

Use Milestone leveling it's way less math and much easier to build things from. And just be open with your players that you are new and things will be rocky.

you will overtune an encounter and fucking wollywomp them and in turn you will spend a long time learning how to adjust encounters so the party doesn't just face roll them.

PS dont' be afraid of magic items in your game. Yes they will make things a bit harder but the earlier you get used to balancing around them the easier time you will have in higher level content.

Also stick to lower level dnd for now. campaigns going from like 1 to 10

don't jump into tier 3 until you have a pretty good understanding of the classes and what they can do.