Welcome to TFP. Good to have you stop by.
This article is helpful:
Pool School - Guide for Seasonal/Temporary Pools
The first step is to add cyanuric acid (aka CYA or stabilizer). Do either #1 or #2 below, but not both. Your pool will need 1 lb of stabilizer one way or another and you will not need to add it again unless you drain the pool. This protects the chlorine from burning off quickly in sunshine.
1. This may be in your kit, but the only way I could know is if you list everything that is in the kit. There may be pucks of stabilized chlorine and a floater to put them in. This will work for a short period of time until there is enough stabilizer in the pool. Follow the instructions that came with the starter kit.
2. Ignore the kit and follow these instructions, based on Trouble Free Pool Care which is safe and reliable and what we use here at Trouble Free Pool:
Buy 1 pound of stabilizer. Put it in an old sock, tie it closed, and then with rubber gloves on, hold it underwater and squish it around and it will come out as a whitish cloud. Hang it in the pool to give it a rest, then come back and squish some more, repeat, repeat, until it is all dissolved. If you see any on the bottom, sweep it around
Buy some plain, unscented bleach (not the splashless type) with a concentration of 8.25% sodium hypochlorite. Add two and a half cups to your pool and sweep it around.
Test the pH. If your pH is above 7.8, add a quarter cup (2 ounces) of muriatic acid (MA). Wear gloves and safety glasses and stay upwind when you measure and pour MA. You will notice if you breathe it, it will startle you, and you will learn to avoid breathing the fumes. Fumes are not harmful beyond the time while you feel it. Rinse everything in the pool afterwards. If it splashes on you or anything, dilute it immediately by rinsing it off.
If your pool pH is 7.8 or less, do nothing more.
When you reply, tell us what strength the muriatic acid is - might be 15.7% might be 31.5%, might be some other %. The amount I recommended is based on 31.5%
If you have a test kit, tell us what it is. If not, get a 5in1 such as an HTH, that tests at least pH, free chlorine, and total alkalinity. An alternative is to buy a good kit and fully know everything going on in your pool. The TF100 is the favorite here and you can get it from
TFTestkits.net for $70
That should cover it for now, and have fun with your pool. What I described will allow you to use the pool if warm enough!
If you want to fully take charge of your pool, in addition to the seasonal pool link, start reading pool school, which is not all that long, but it does cover a lot. Feel free to ask any questions you like. Other people here will help you along as needed.