how can I freeze the top TWO rows

In a spread sheet I use the top row as a title and the next row as headings for the columns and want to freeze these two rows

The former explanation to go to windowsis inaccurate. These are the proper steps in LC, as found in the LC instructions, properly instruct you to go to the view tab rather than the windows tab

Fixation of cells of header
Select the reference cell

View Menu > “Freeze cells” > Freeze Rows and Columns
The cells above and to the left of the reference cell will be fixed.

In Addition:

Freeze rows and or columns in Calc LibreOffice 6.4

From Help (F1)

Freezing Rows or Columns as Headers

If you have long rows or columns of data that extend beyond the viewable area of the sheet, you can freeze some rows or columns, which allows you to see the frozen columns or rows as you scroll through the rest of the data.

  1. Select the row below, or the column to the right of the row or column that you want to be in the frozen region. All rows above, or all columns to the left of the selection are frozen.
    To freeze both horizontally and vertically, select the cell that is below the row and to the right of the column that you want to freeze.

  2. Choose Window - Freeze.
    To deactivate, choose Window - Freeze again.

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Awesome! I kept selecting the row containing the headers and was getting nowhere! After selecting the row below that, now I finally have what I want! Thanks so much!

You might want to mention that you are not referring to the Window menu item, since there is no longer a freeze option there. There is a button on the toolbar called Freeze Columns and Headers.