The application process is pretty simple, you need to provide a few pieces of information:

• The DNS subdomain for vyos's pool (i.e. <subdomain>.pool.ntp.org). My guess is that this would be vyos.pool.ntp.org. There will then be [0123].vyos.pool.ntp.org.
• pool client specifics (what types of devices will use the pool, how often will they poll (by default), etc.
• order of magnitude of the number of devices using the pool (from < 1k to < 100M).
• Contact details for the pool admins to contact if there are issues.

In my experience, this will take one or two days to get the approval of the new pool name. At that point, the project would just set the default NTP/Chronyd config to use [0123].pool.ntp.org Those names will dynamically resolve to any currently in-pool ntp server.