Getting Nervous... New Tank

[dccstl]

I recently just set up a brand new tank for a school I work at. Cleaned it, put all new stuff in (left a little old water), and a new filter (Fluval 406) etc. I went to the fish store and told them all of this and they recommended I start with 3 goldfish for the 75 gallon tank because it had to cycle. They told me a little about this cycling process but now I am second guessing putting any fish in like they said.

I check the levels when I get to work and when I leave. After the first day the water looked cloudy. The PH appears to be around 7.0-7.2. The ammonia is right around .25 maybe a little under and it is the third day. The sold me ammolock but I have read not to use it.

Nitrate/Nitrite are at 0.

I now understand that I should have waited for the fish tank to cycle before adding fish but it is too late.

So here is my question. Should I act now with an ammonia level just under .25? When should I use ammolock? If I do water changes how should I prepare the water (besides temp and water conditioner).

I will not feed them but every three to four days. Thank you for the help in advance.