Sync to existing S3 resource

I am new to Serverless. I have been able to use it to configure a custom domain name with API Gateway serving from an S3 resource. So far, so good.

Now I want to sync my local files with the S3 bucket. How do I configure a sync for an existing bucket resource? I’ve been trying various permutations but mostly I end up making a mess and having to delete everything manually before starting over.

For now, I find the name of the bucket and use “aws s3 sync” to do the work.

I am really new to this and missing basic concepts so you are quite welcome to spell it out for me. Pointers to where I should have located this information are also welcome.

Thank you.