First off, head on over to Generate Randomize Game and provide your ROM. Once you've got a randomized ROM, you need a way to play. There's a couple options for that...
An emulator is a program that closely replicates NES hardware, allowing you to run NES games on your computer.
Playing a randomizer seed on original hardware requires a "flash cart", which is a special cartridge designed for that hardware that allows you to put the randomized ROM on some kind of portable flash memory (usually an SD or MicroSD card) which is inserted into the flash cart, which then goes in the original console.
Many people in the community consider the Everdrive N8 to be best NES flash cart on the market right now. You can learn more about it, download the firmware, and find a shop to buy one on their website here.