Click "File" in the top left corner, select "Open", navigate to the RDR1 directory and open the "game" folder.
Select the file "mapres.rpf".
Find a file called "swall.wtd".
Right click on "swall.wtd" and select "Replace file".
In the replacement window that opens, click on the three dots icon (...), navigate to the file you extracted from the archive, and select it. Click REPLACE.
Press "Ctrl + S". When the message “Are you sure you want to save the Current RPF?” appears, click “YES”.
Wait for the rebuild process to complete. Once completed, close the application and launch the game.