Unable to merge tracks

I have a windows 10, and I am having a lot of trouble trying to merge tracks two audacity files. I understand that in order to open two files on one you would go file>import>select files>enter, but then I get the error message that is attached below. I have looked into then going to open files and selecting multiple files but they load into different windows. I cannot even drag and drop the files. If anyone has some advice on how I can merge these two files or something I need to do in my setting, please let me know, thank you!
Audacity .png

Open one project and export as a WAV file.
Close that project.
Open the other project and import the WAV file.

What steve says is the preferred way.

You can also copy selected tracks(s), or portions thereof, from one audacity project to another. See also: https://manual.audacityteam.org/man/edit_menu_copy_paste_and_duplicate.html

I hope this helps. :smiley: