There's a lot of things you need to consider that if you don't give importance your investment may be at risk so here are some of the things ou need to consider or to study.
Learn about the basics first such as:
Bitcoin wallets
How Bitcoin works
What is Blockchain
Types of wallet
And different kinds of investments
Second Learn what kind of investments you need to do, here are:
Trading
Holding
When you've decided what kind of investment you're going to do start finding exchange where you will bought your first bitcoin there's a lot of platforms where you can buy bitcoins such as:
LocalBitcoins
Binance
Coinbase
Just search on the internet.
NOTE: You should know the risk you're going to face when it comes to investment remember that there's no assurance that if you invest you're going to earn so invest only what you can afford to lose.
Some people think investing in bitcoin is east but little do they know that earning here is like being on a cliff hanger. You don't always get the certainty of earning profit since failure, scams and frauds are everywhere. You need quite plenty of knowledge here since bitcoin is a very complex investment. Being smart and wise on your investment is much needed here also.