Welcome to TFP!
There are two articles you should read:
Using Bromine in a Spa and
Using Chlorine in a Spa. Using a product such as Spa System Flush for a new spa is essential to remove biofilms though superchlorinating at very high levels (around 100 ppm) can also be effective.
Spas are much lower in water volume than pools so the bather load is much higher than in a residential pool. At hot spa temperatures (104ºF) one sweats a lot and one's sweat and urine as well as dead skin and body oils creates a fairly high oxidizer demand. A rough rule-of-thumb is that every person-hour of soaking in a hot spa requires around 3-1/2 teaspoons of Dichlor or 5 fluid ounces of 6% bleach or 7 teaspoons of non-chlorine shock (43% MPS). This rule-of-thumb assumes you do not have an ozonator. With an ozonator, the amounts needed are roughly cut in half (usually). If you are using bromine, then the bromine tablets are just there to maintain a consistent sanitizer level when not soaking in the tub. You should create a bromide bank (by adding sodium bromide initially) and use an oxidizer such as Dichlor, bleach, or MPS to create more bromine to oxidize the bather waste after a soak.
Many people do not like to have higher sanitizer levels during their soak since the smell can be annoying to them so most people add the sanitizer/oxidizer after their soak in sufficient quantity such that they measure a residual by the next time they soak. If you are only soaking for an hour, then this is probably OK since any bacteria you shed won't reproduce very much and the high level of sanitizer added after the soak should kill anything at that point (assuming you are using enough). If you have a long party, however, then it would be better to add more oxidizer periodically to keep up with the bather load (or you could add a lot up-front, but people may not like it during their soak).
Richard