Bringing media in
Open Media
Open Media in the Media Bin, or File → Open Media, or Ctrl+O. Pick one file or several. The dialog remembers the last folder you used.
Your first import behaves differently from every one after it. The first files go straight onto the timeline so you can press Play immediately. Everything after that sits in the bin until you place it.
The two Add buttons
Each entry in the bin carries two.
Add to Timeline appends the file to the end of the existing material on a matching track. The status bar says "Media appended to the timeline."
Add on New Audio Track creates a fresh audio lane and puts the file at zero on it. This is the one you want for a music bed, because it starts where the piece starts and it does not fight with the audio already on the timeline.
To put something somewhere specific, drag it from the bin onto the lane and position you want. Video goes on video lanes, audio on audio lanes.
What arrives when you add a video
A video with sound arrives as two clips: the picture on a video track and the sound on an audio track, linked. Moving one moves the other, which is what keeps them in sync while you rearrange.
Right click either half to unlink them when you want to slide the sound separately, which is how you build a J or L cut. See Sound for what those are and why they matter.
Mixed first imports
If your very first import includes both video and audio files, the audio ones land on their own track rather than being stacked under the video. That is deliberate. A music file and a camera file are not the same kind of thing and they should not share a lane.
Photographs
Still images can be added like any other file, and they arrive with a default duration you can trim. For a sequence of photographs with a soundtrack, use Tools → Images to Video instead, which handles the timing and the crossfades in one pass. See The tools.
What the bin tells you
Duration, dimensions, codec and frame rate, before you place anything. Two things there are worth reading every time.
The frame rate, because mixing rates in one project is the usual cause of sound that drifts away from picture over a long piece. See Frames, time, and why the numbers are strange.
The codec, because a file the preview engine cannot decode will still export correctly but will not play smoothly while you edit. If a clip behaves oddly in the preview but is fine in the export, that is why.
Missing media
The project file holds your edit decisions and references to your footage. It does not hold the footage. Move, rename or unplug a source and the project cannot find it.
When that happens the affected entries are marked, and the Add menu refuses to append them with the reason "Restore this missing source and reopen the project first." Put the file back where it was, under the name it had, and reopen the project.
The way to avoid the whole problem is to keep your media in a folder next to the project file and move the two together as one thing.