Re-connecting audio track to video?

Hi, I am having problems with occasional video's where the audio is dead. The video runs OK but wit no audio. When this happens I remove the audio track from the video track by clicking on the chain-link Icon and deleting the original audio track from the video. I then separate the audio and video and insert the new audio track back underneath the remaining video track. My question is how do I then lock the audio and video together again? I thought by clicking the chain link icon so that it lights up that would do it, but no, so any advice on how to complete this action would be more than appreciated. Please ignore this request, I have posted in the wrong forum. Silly me, what I call a senior moment. I would, however, like to know if there is a way to delete a post when silly mistakes are made?