This might be a part of a longer series.. too early to say. Anyway heres the first few common problems beginners have with Blender Video Sequence Editor(VSE)
Where is the VSE editor?
Use the screen layout dropdown menu on the top bar to switch to "video editing". refer image below
When video clips are imported, the audio and video strips are of different lengths!
heres what you do.. before importing the video, check its properties for frame rate.
In blender match that same framerate for your project. Now when you import the file, both audio and video strips will be the same length.
When you export video.. theres no sound?!
Heres what you do, when you set the output format, certain formats will not give you the option to st "encoding" for audio. select the ones that do.. like xvid, mpeg etc.
then under this new Encoding area, you will be able to set a codec for audio.
I just use the presets.. it automatically sets appropriate video and audio codecs for you