As of now its seen that such email was for tier 2 and 5 category.
Ideally, you should get an email for resuse of biometric or to book an appointment. Wait for such email as they haven’t started sending out such emails for July applicants yet, most likely in a week or couple you might get one.
Meantime, you can upload the documents and use the submit to UKVI option to submit the documents only if you are completely sure that your documents are accurate as it can be done only once. Later you can upload more document but cannot submit on your own, at the time of your appointment UKVCAS agent can submit the documents to UKVI that are uploaded later