Buying bitcoin is easy if am being honest with you, you simply need to get some basics in place before that
1. Does your country allow the purchase of crypto currency?
2. Do you have a bitcoin wallet yet? If no, you can download coinomi or trust wallet, or you purchase a hard wallet like trezor or Guarda
3. There are several ways to buy bitcoin, you csn get it on Crypto currency exchanges like binance, coinbase or even coinomi, you can also get it from trusted escrow groups where your friends belong.

The basics to buying bitcoin is easy, ensure you copy the right deposit address, remember to back up your wallet.
Never share your private key with anyone