If you do not have an electronic control system on your pool/spa equipment system, you have to go out and manually turn your valves in order to use your spa. This article provides some general direction in this area.
Every pool is different and these articles are designed as a general guide. As always, if you are not sure of what you are doing, get a pool professional involved who can answer any questions you have and give you professional onsite advice.
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In spa mode, on the intake side. the spa drain is open and the pool drain and skimmers are closed.
Notice that it is not necessary to close off the individual pool intakes (skimmers and pool drain), because you can just move the 3 port valve to open up the spa drain and close off all the pool intakes all at once.
On the return side, the spa jets are opened and the pool returns and water feature are closed.
Again, it is not necessary to close off the individual pool return valves because the three port valve on the return side will open the flow to the spa jets and close off the flow to the pool returns all at once.