Hi:
I suggest you go back to the Programming 1 class and review the material on using PROC IMPORT. When you are importing from a multi-sheet workbook, PROC IMPORT expects the OUT= to be a SAS dataset. The Excel Workbook is the equivalent of a library containing multiple tables (one table for each sheet). So a single SAS dataset is all that the OUT= option is going to create.
Are you working in Lesson 2? There is a demo in Lesson 2 that you should revisit, as shown below:

In this demo, the instructor uses the XLSX LIBNAME engine to run a PROC CONTENTS on the entire workbook and then, after reviewing the PROC CONTENTS output, she shows how to point PROC CONTENTS to a single sheet in the workbook --also using the LIBNAME engine. PROC IMPORT is NOT used in this demo, at all.
In Lesson 2, PROC IMPORT is used to read a tab delimited file and a CSV file -- but you cannot use the XLSX engine to read either of those types of "raw" or "unstructured" data files.
Please clarify exactly in the course where you are working by providing the title of the Lesson, demo, activity or practice you're working in. Most of the activities and practices have code that you can reveal when you're following the instructions. Usually you can compare your code to the solution to see what you've missed. If you're trying to repeat the demo in Lesson 2, you're not following the demo steps.
Cynthia