The submission period is from July 1 through July 31. The deadline is July 31st 11:59 pm (JST), 2:59 pm (UTC), 10:59 am (EST).
On June the "VketTools" will become available, from which you can install official Prefabs.
You need to do both Unity Submission and Web Submission.
In the Unity Submission you can submit your data on Unity using the VketTools, while for Web Submission you can submit a glb file or VRM file via the website.
During the Submission Period you may check how your product will actually look from the Preview World, to be updated on a regular basis.
For details please refer to the Unity Submission Rules or Web Submission Rules.