Merging seprate audio files

I am using Windows seven with Audacity 2.1.2.

I record many cassette tapes for a University l library. I record side A and save it as a 24 bit wav file named XXXA. I then record side B and save it as XXXB.

Often I need to combine the two files and save as XXXAB.

The technique I had used to merge such files with previous versions of Audacity do not work with this latest version.

How can I merge such separate audio fines in Audacity 2.1.2?

Import both files. They appear as two tracks, one above the other.
Align the tracks end to end (see:
Export as “XXXAB”.