There are several options to purchase Bitcoin with fiat currencies like USD and other cryptocurrencies.
All you need to do is log on to the website or platform where you have your account and choose the digital currency you want to purchase.
Now choose the currency in which you are going to make the purchase and the amount for which you will make the buy. Review your wallet address cautiously once and click Continue.
You can also buy Bitcoin from the Bitcoin.com wallet
Open the wallet on your device. Click on the Buy button for BTC. Follow the instructions to deposit coins in your wallet and verify your identity. As the transaction gets completed, you will get the coins in your account.
Another way to purchase Bitcoin is via peer to peer trading platform
Make an account on an exchange and find a seller that is ready to sell at your buy order.
Start the trade and the seller will send the coin to escrow account.
After you have made the bank transfer and the seller confirms receiving, then your digital currency will be released from the escrow account and transferred to your digital wallet.
To know more about how to buy and sell bitcoin and many other details you can check online for various other sites.
You can sell Bitcoin and get other crypto coins as well as fiat currencies like USD.
On peer to peer trading platform
Find a buyer who will purchase your coins at your created sell order. Now open the trade and send your coins to the blind escrow account.
After the buyer has sent you the payment via bank transfer, and you have confirmed the receiving of the funds, the sold digital currency will be released from the escrow account and transferred to the digital wallet of the buyer.
On a cryptocurrency platform
Go to a cryptocurrency exchange, open an account, and verify your identity. Follow the instructions of the site to sell your coin.
If you are selling it for fiat money, then the funds will get deposited in your bank account. If you want to sell it for another cryptocurrency, just send the coin to your wallet.
Make sure that you check if your wallet accepts the coins before you send them.