How soon should I start seeing bacteria on my Petri dish?

Usually within 24-48 hours you should begin to see bacteria growing. It might depend on what you used as a source of bacteria, but most common ones will grow nicely on agar plates in 1-2 days.

it depends on what nutrients are in the agar

you may have just plain agar with nothing in it

although things can still grow on that, but it shouldn't take 6 days

if you want it to grow faster, put it in an oven at 37°C (98.6°F) which is the normal temperature the bacteria would be growing in

they should come up within a day or two, bacteria grow very fast

try to use sterile technique and store the petri dishes upside down in the oven so that moisture doesn't drip down on the agar

you should probably get more than 1 or 2 colonies, yet if you do it wrong and not use sterile technique you may end up with a lawn of bacteria over the entire dish....