There are lots of ways to do this.
The question is: how do YOU want it to do this and when?
You can have a "control" sheet, or "summary" sheet that
has a button that you hit when you want to combine the workbooks.
You can make it so that it automatically does it when you OPEN the workbook.
You can make it so that it automatically runs, but prompts the user if he/she
wants to refresh or update the data... you can make it so that it only does this
if the user is one of a list of users...
As you can see, there is a myriad of possibilities.

the next question is: are both worksheets  formatted the same?
Same columns, etc...

Where do you want the resulting workbook to reside?

Let's say the answer is:
You want to have a third workbook, a "summary" workbook, that has
a button at the top of the page, used to refresh the data.
The refresh button first deletes the contents of the current sheet,
then copies the data from the first workbook to the sheet.
then, it opens the second workbook and reads through the data, checking
for existing records. If no existing record is found, then it copies the data
to the end.

Once complete, it sorts the sheet and saves the file.

How's that?