Each post has an 'msg' anchor, hidden under '#' sign above or near the message. Mouse over it, copy link location and you could use it in your messages. For example, for this
message the link could be:https://www.minibb.com/forums/how-to-2/how-to-give-permalinks-to-specific-posts-902.html#msg5569
Alternatively, you could install the "Advanced Anchors" add-on
, it's free and it will allow more stronger and sophisticated hyperlinking to certain messages, using "message locator" script, which will be substituted for the '# sign.