The only thing that I can think of, is that you need to clean it very thoroughly.
I think you can either get specialist cleaning products, or you may still be able to get methylene blue from an aquarist. I've used methylene in the past and you just follow the instructions for your particular tank. It needs to be very thoroughly washed out though, as methylene is toxic to fish [no, doesn't make sense to me either
].
You will need to know how much water your tank can hold in litres. Mine is about 18 x 15" and holds 35 litres, so that should give you an estimate. Otherwise it will be fill a bucket and see!
After that you will need gravel for the bottom [several kilos!] and plants. Now I operate a coldwater tank, so I use plastic ones but it is possible to use real plants in a heated tank. Just remember that they will need looking after as well. The water will need to be dechlorinated prior to filling the tank. I use Aquasafe and usually leave it for 6-8 hours before using it. Just mix it into the first bucket and then continue filling with tap water. Leave the tank to settle for about 4-6 days the first time, as you get 'fog' from the gravel and it will let the filter settle down. You can get a biological booster for the first filter use, but I don't bother with coldwater species, tropical might need it though.
When it comes to deciding upon the fish, the best thing is to go to a specialist aquarium shop, tell them the size of your tank and let them help you to choose. Besides fish, you might want some of those bottom feeder things, to help keep the tank clean.
HTH.
Jan.