From the post reply that's added? If so, remove the "%lock_time%" quick tag from the post template and it won't add a lock time.
This plugin only uses the internal lock topic option, so any work around for posting in locked topics will need to be done within IPB4 itself. I believe there is a group permission to allow certain member groups to post in locked topics still.
Have you setup your plugin settings? Has the auto lock topic ran yet? See acp > system tab > advanced configuration > view tasks > look for auto lock topics entry.
This doesn't provide an auto lock setting per topic. If you check the plugin settings, you select the filters and which forums and it mass locks topics for you in the background using the filters you selected.