You mean your prostate? Firstly you gotta be lubed and relax. Take a shower beforehand if itll relieve any anxiety about making a mess. Then once youre nice and comfortable on your bed, apply plenty of lube and explore with your fingers.
Your prostate is towards your front (where your dick is) and a few inches in, like up to your second knuckle.
Its also not an instant pleasure spot like your dick would be, it takes a while to build up to the pleasure a bit. I recommend, abstaining for a few days to let the horniness build then edge for an hour or two to help with that before you start prostate play.