This procedure applies to moderators/administrators only and to all comments in general. Comments need to be dealt with as soon after they arrive as possible. This is especially true of forums if they are to be kept alive.
Go adminster > comments to obtain theview shown below. Then select the Approval queue tab.
Comments subject to a queue are listed here. Unfortunately each one needs to be checked, to confirm the content is acceptable (see notes on Netiquette). Tick those comments you approve, using the tick box, adjacent to each comment. When finished, make sure the update option is set to publish selected comments (the default) and click update to publish them.
With any remaining comments, you have the option to edit the comment itself. maybe to paraphrase those which are unnecessarily long winded. When finished tick those that now met the sites guidelines, and when finished publish these.
The remaining comments are probably those which are to be deleted. Change the update option to Delete selected comments and tick them. You may wish to make a note of the users, should further action be necessary to possibly bar them from the site for instance. Lastly click the update button to remove them.
Closing down a forum topic
When a discussion has run its course, and you don't want to attract further comments/replies. select the edit option on the forum topic itself and switch the comments section to read only. This also removes comments/replies option from all the attached comments/replies as well.
You may choose to leave the topic in place, for a short period, before arching it.