Remove the black ink cartridge from your printer and install a white on black cartridge. You can find one at most arts and craft stores. The ink cartridge will be labeled as to what black ink cartridge or computer it is compatible with.
Remove the printer paper from the printer and insert the black cardstock. The cardstock is thicker so you can't place as much of it into the paper tray.
Open the program you want to print from and load the document.
Click "File" followed by "Print" and allow the content to print on the black cardstock. You are going to see the white text appear on the black paper.