Learning to scuba dive is surprisingly straightforward. You don't need to understand diving equipment, memorize certification requirements, or decide what kind of diver you eventually want to become. You simply need to find a good instructor, purchase a few basic pieces of equipment, and complete your Open Water certification.
There are plenty of decisions to make later, but getting started really comes down to three steps.
Your First Three Steps
Step 1: Choose a Dive Shop and Instructor
Your first instructor will influence almost everything about how you learn to dive. They'll introduce you to the equipment, teach you how to control your buoyancy, and help establish the habits you'll carry into future dives.
I would prioritize instructor quality over convenience, price, or certification agency. Look for smaller classes, plenty of practice time, and someone who is willing to slow down when students need additional attention. You should feel comfortable asking questions before you've even enrolled.
Step 2: Buy Your Basic Scuba Gear
You don't need to purchase a complete scuba setup before learning to dive. Most shops provide rental regulators, BCDs, cylinders, and other equipment during training. You'll typically be expected to purchase a mask, fins, and possibly a snorkel, depending on the program.
Of those purchases, I'd pay particular attention to the mask. A properly fitting mask makes learning considerably more comfortable, while one that constantly leaks can make even simple exercises frustrating.
My advice is to buy the basics and rent everything else. You'll have a much better idea of what equipment you actually want after you've spent some time underwater.
Step 3: Complete Your Open Water Certification
Your Open Water course generally consists of three parts: academic learning, confined-water training, and four open-water certification dives.
You'll learn the principles of scuba diving, practice essential skills in a swimming pool or similarly controlled environment, and then demonstrate those skills during actual dives. Depending on the program, training might take several consecutive days or be spread across multiple weekends.
Don't worry about knowing how to dive before arriving. That's what you're paying the instructor to teach you. What matters is receiving enough instruction and practice to demonstrate the required skills comfortably.
