In general you get the embed code from the site, then inspect it to see if it has an easily replaceable ID for the content.
Then you need to construct the data for the entry in the ACP.
In some cases it will require a PHP callback or add-on.
Manually copying them shouldn't be necessary. You can "Rebuild master data" by going to install and it should re-add the missing ones (they're part of our add-on data output now, so no longer require manual work to restore them).
Manually copying them shouldn't be necessary. You can "Rebuild master data" by going to install and it should re-add the missing ones (they're part of our add-on data output now, so no longer require manual work to restore them).
There is a change in XF2 with regards to media sites - rebuilding the master data will add the default ones back in if they are missing - that didn't happen in XF1.
You can run the rebuild and any still missing will be created.
There won't be any downtime - it should take a minute or so.