In most cases, you just upload the app, follow its unique setup process to add your devices, and you're good to go.
The more time-consuming part may well be choosing the right app for you. Most importantly, you'll need one that works with both your type of phone and the device or devices you want to control.
Beyond that, look for features, including multiple uploads for use on many family members' smartphones, a physical remote (for when Grandma or the babysitter is over), and convenient programmable automations, such as turning the TV on when your favorite show starts or muting it when your phone rings.
Here are some popular apps to explore: