Summarize:

Measure the average depth of your pool. Next, multiply your average depth by the width and the length of your pool in feet, then multiply that number by 7.5, the number of gallons in a cubic foot.  If you don't know the average depth of your pool, add the depth of the shallow end and the depth of the deep end and divide by 2 The formula for volume is Average Depth x Width x Length x 7.5 = Volume in gallons Salt systems can vary widely in price and features, but the basics of what you need are the salt generator, which uses electricity to break down the salt into chlorine, and a control unit, which allows you to monitor the system. Make sure you purchase a system for an above-ground pool. You can purchase a saltwater generator at any pool supply store. The system will cost between $150-$700 USD depending on the size you need and the features you choose. The system you purchase should be rated for a pool about 10% larger than the one you own. This will keep your system from having to operate at full capacity all the time. The instructions on your system will tell you how much salt to use in your water, and it will be based on the volume of your pool. Saltwater pools are usually a salinity of about 3500 ppm. Wait a full day before installing the saltwater system. You can purchase pool-grade salt from a pool supply company. A 40 pounds (18 kg) bag of salt usually costs about $5 USD. Make sure you turn off the power to the pool by flipping the circuit breaker on your electrical panel. The specific installation instructions will vary depending on the model you chose, but it should be the last piece of equipment attached to the pool pipe before the water returns to the pool. Since you will be working with electricity and water, you may want to have this step performed professionally if you’re not comfortable with electrical equipment. The control unit is wired to the saltwater generator, allowing you to easily adjust the levels of salt in your pool. Read the instruction manual that came with your system to determine exactly how to install the control panel. Some models are as simple as mounting the panel on a nearby wall or fence, while others may require you to hook up the wiring yourself. When metal is submerged in saltwater, it creates an electrical charge similar to a battery. This process will corrode the metal in your pool. Because zinc corrodes faster than other metals, you can place a piece of zinc known as a sacrificial zinc anode in your pool to slow the corrosion of the other metals. You will need to replace your sacrificial zinc anode 1-2 times a year, or when the anode is about half of its original size.
Measure the volume of your pool if you don’t know it. Purchase a saltwater generator and a control unit. Choose a larger system than you need. Add salt to your pool and let it sit for 24 hours. Install the saltwater generator into your pool’s existing plumbing. Install the control unit somewhere close by your pool. Add a sacrificial zinc anode to prevent galvanic corrosion.