Start with the cover and the water test.

Yes, but don’t shock it yet. First, pull the cover off carefully—don’t dump a pile of dead leaves into the water. Hose it off, let it dry, and store it. Then check the water level. Top it off if it’s low.

Next, test the water. Grab a test kit or strips and check pH, alkalinity, and chlorine. Get those in range before you do anything dramatic. If you shock dirty, off-balance water, you’re just wasting shock.

Once the chemistry is stable, then you can scrub the walls, vacuum, and start running the filter. One step at a time. Getting the balance right first saves you from fighting cloudy water for weeks.