This may be a silly question but as this is my first time harvesting pototatoes I wanted to know from the experts... When and how do i know they are ready to be uprooted.

In Reno, NV

We don't harvest them here until the top part of the plant has died. As long as it happens before the first frost, we dig them out then.

I agree. When top is died back.
😎😎😎

It somewhat depends on your own preference -- if you want smaller "new potatoes," the general rule of thumb is you can start digging them when the plants begin flowering (although I've grown some potato varieties that never did flower, so then it's more of a guessing game). If you want the largest possible potatoes, then wait until the tops die back. Or dig some anytime in between those two "mileposts" to cook up for supper.

If you have planted enough for long term use, let the ones to be stored in the ground for several weeks after the tops die off but it is best to mark to some degree where the plants are as the tops can totally disappear and you will spike some when you dig.

That said, it is still best to dig a goodly amount away from the vine when you dig as they often have potatoes out in the badlands just to annoy as you dig by spiking or cutting one in half if you let them in the ground long enough for storage.