Once you've selected your clip, drag it to the Timeline, and drop it where you want. You can also use the drag and drop method to insert or overwrite footage into an existing sequence in the Timeline. If you drag your clip to the top third of the video track, you'll see an arrow that points to the right. This means that when you drop your footage it will be inserted into the existing sequence. If you drag your clip to the bottom two thirds of the video track, you'll see an arrow that points down. This means that your footage will be overwritten into the sequence, replacing the video in your sequence for the duration of the video clip.