In order to download a module you have built to your Nexys 4 board, you must make a bitstream file. Be sure that you have first added an XDC file to your project as it is what makes the connections between your design and the board's inputs and outputs. If you have more than 1 XDC file, right click the ones you don't want to use and click disable. You can re-enable them later when you want to use them.
You can download a bitstream file to the Nexys 4 board right in Vivado.
Once your bitstream is downloaded to the Nexys 4, test it. If your tests determine that everything went well, you'll want to make a copy of your bitstream file so that it doesn't get overwritten by generating another bitstream by following the steps below.
<lab name>.runs / impl_1
..bit
file. .bit
file to the Bit Files folder you created in step 1.