There is not a simple way to mark a block of messages as read. Basically you need to open those in the notes list and then click on each one. The challenge is getting the list to be filtered with just the Unread + Resolved messages. In a future version of Paratext there will be a better way to create filters of mixed status, but currently you can only do this by editing a filter file outside of Paratext. Here is a quick video that explains how to create a filter for Unread and Unresolved notes, but the process would be the same for Unread and Resolved.
Once you apply the filter to the notes list you would simply click each note.