How to stick an audio file just after another one ?

Sorry if the question seems obvious but I can’t find the way just, at the end of an audio file added in Audacity, to add another one, so that I can “stick them” and they form only one audio file.
When I drop a second audio file in Audacity, it comes under the second one…

Thank you very much for your help

Audacity is a “multi-track” audio app, so it’s perfectly OK to have multiple tracks in a project. When you Export from Audacity, all tracks (provided they are not muted) are mixed together. All that you need to do is to align the tracks so that they start one after another. You can do that either by using the Time Shift Tool, or by selecting All tracks (Ctrl + A) and then “Tracks menu > Align > End to End”.

Note that you can also drag the audio from one track to another using the Time Shift Tool, but only into a space that is big enough for the clip that you are dragging.