Hi Steve and welcome to the forum
First thing to do is contact your water supply company and find out what the GH (general hardness), KH (carbonate hardness) and pH of your water is. This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).
Depending on what the GH of your water is, will determine what fish you should keep.
Angelfish, most tetras, barbs, Bettas, gouramis, rasbora, Corydoras and small species of suckermouth catfish all occur in soft water (GH below 150ppm) and a pH below 7.0.
Livebearers (guppies, platies, swordtails, mollies), rainbowfish and goldfish occur in medium hard water with a GH around 200-250ppm and a pH above 7.0.
If you have very hard water (GH above 300ppm) then look at African Rift Lake cichlids, or use distilled or reverse osmosis water to reduce the GH and keep fishes from softer water.
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After that, read up on cycling an aquarium. Good luck
Fishless cycling https://www.fishforums.net/threads/cycling-your-new-fresh-water-tank-read-this-first.421488/ Silent or plant cycling https://www.fishforums.net/threads/planted-silent-cycling.470400/ Fish-in cycling...
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