Hello and welcome.

Since you are new to pools, we probably should bring you up to speed on a couple very important items related to your question. First, we here at TFP highly discourage the use of tablets because they tend to raise your CYA (stabilizer) level to an unmanageable level. Before you know it, you will have no choice but to do partial drains of the pool to replace the water which is the only way to lower CYA. When you need to raise free chlorine (FC) do it with REGULAR liquid bleach. Generic from Wal-Mart of HEB is fine. About $2.98 a jug. Pour it in slowly at your return jets with the pump running for at least 30 min and you're fine. Easy. You should also be familiar with this list of
Pool School - Recommended Pool Chemicals for your pool. This is ALL you need.
Next, 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. You’ll have a happier pool, spend less time maintaining your pool, and probably save some $$ in the process.
As for your in-chlorinator, on the rare occasion you may need to use it (like on vacation) you simply adjust the output with that small knob at the bottom. Mine has the same thing. The larger black 2 & 3-way valves distribute and/or shut-off water to other areas such as a spa, water feature, skimmer/main drain, etc.
And finally, make sure you have one of the recommended test kits (TF-100 or Taylor K-2006) as well (link below). It is an absolute “must” to obtain the proper chemical readings before you can treat your pool. Accurate test readings serve as the foundation for everything you do from this point forward and the advice you receive on this site. Test strips and pool store tests are unreliable at best.
Welcome to TFP!