There are a number of ways you can get Bitcoin:
Just like traditional money, you can earn it by providing goods or services, and asking for people to pay you in Bitcoin rather than in traditional money. This is often a cheaper and easier alternative to other payment methods and one of the easiest ways to get your hands on some Bitcoin.
Another way is how most people get their Bitcoin: buy it from a credible Bitcoin broker or exchange provider, like Luno. This is similar to how you would buy foreign currency at your bank or shares online. This is often the easiest way to get Bitcoin because you are virtually guaranteed that someone will be willing to sell their Bitcoin to you on such a platform.
You can also get Bitcoin by mining for it, but this has become very difficult to do for the average person. Most mining is now done by huge companies with very expensive and highly specialised equipment, which a typical person or computer cannot compete with. So unless you have a lot of expertise and a huge amount of money to spend on this, rather just buy or earn the Bitcoin.