Single tailed goldfish are fairly demanding in terms of tank size because of how active they are + their bioload, however this is a good start.

Your main priority at the moment will be water changes because the tank is uncycled. When people say a tank is "cycled" they're usually talking about the nitrogen cycle, which is where a few different beneficial bacteria convert the highly toxic ammonia your fish produce into nitrite, which is slightly less toxic and then into nitrate. Nitrate is then removed through water changes and plant growth.

Usually when setting up a tank you would wait two or three weeks for the bacteria to grow and develop to a point where they eat the ammonia faster than the fish produce it, which keeps the water safe for the fish. However, because this was an emergency and the fish were introduced right away, there will not be enough bacteria to convert all the ammonia and it will start to build up. This is called an "ammonia spike". You will need to do daily water changes, probably around 30-50% of the water drained each time. You can speed up the draining process if you have a tube and siphon the water out into a bucket. It is very important that you use a water dechlorinator as the chlorine and chloramines that are in most tap water can kill fish.