Welcome! Golden rule - Avoid the pool store for testing, advice, or products. You simply won’t get the advice/service you deserve and you will waste money on products your pool doesn’t need. Do not add anything to your pool other than what is advocated by the TFP site or its experts if you truly want to follow the TFPC method. You’ll have a happier pool, spend less time maintaining your pool, and probably save some $$ in the process. The following are short articles from this site that you will see linked in my signature below: Pool School, Recommended Levels (for YOUR pool), PoolMath Calculator, SLAM, and the Chlorine/CYA Chart.
FYI, here's a little excerpt about TFP's "SLAM":
SLAM is the term used when we “Shock” our pool to a higher “Level” of Free Chlorine (FC) and “Maintain” it that way until 3 objectives are met:
1. Water is clear
2. You do not lose any more than 1ppm of FC overnight (that's the OCLT)
3. CC (Combined Chlorine) is <.5
** You MUST meet ALL 3 items above to properly do a SLAM. Simply “spiking" the FC higher than normal isn't SLAMming, therefore there’s a good chance your algae will return.
As Patrick already emphasized - you MUST get one of the recommended test kits.

That's the only way to confirm the readings above that we need to see.