This site will help you clear it. It did it for me at my last pool. Saved me from the nightmare you had at that pool store.
Order one of the recommended testkits online as soon as you can (or find a local store that carries the recommended ones AND check the dates to make sure it isn't near it's expiration date since some stores don't sell many of these more expensive but truly amazing kits)
While it is in the mail you can prepare. Read the links, ask your questions, find local sources for bleach/chlorine (walmart, warehouse store, big hardware store, or a pool store if cheaper on bulk chlorine), and muriatic acid in case you need that. No point in buying anything yet until you get your test kit and see where you stand
You can also check to make sure your vacuum head, vac hose, brush head, pole, and leaf skimmer/leaf rake are all ready for war too, and order/buy whatever you/pool school deems appropriate for you that might be broke or missing.
Don't spend on anything you're not positive you need without asking. Responses are usually very, very fast. Use a cell phone to ask quick questions. Site works well on most smartphones.
You can do this. Thousands before you have