How do you sync an existing local vault using Obsidian Sync? It’s not at all clear what to do.
Should I create a remote vault, and then copy the contents of my local vault into the local copy of the empty remote vault? Or should I do something else?
Create a new vault. Give it the same name as the local vault to avoid confusion. There is no local copy of the remote vault until you connect your local vault to it. You don’t need to move your existing vault or its contents.
Press the Connect button next to your new remote vault. Sync will upload the contents of your local vault to the remote vault. Any changes you make to the vault from now on will be uploaded when you’re connected the the Internet.
On your other device(s), you do almost the same thing, except instead of creating a new vault, you choose the existing one. Sync will download the remote files to the device, and from then on changes to the vault on any device will be synced to the others via the remote vault.