As per your requirement let's keep it as simple as possible.
There are various online services which allow you to buy cryptocurrency like Bitcoin, I will just list those which are credible and easy to use.
>>> Coinbase : Coinbase is a digital currency exchange. They broker exchanges of Bitcoin, Ethereum, Litecoin and many others with fiat currencies in approximately 32 countries, and bitcoin transactions and storage in 190 countries worldwide.
>>> Cex.io : Cex is another Digital currency exchange and one of the oldest. It allows you to buy cryptocurrency with credit card, bank deposit and Skrill etc.
After buying Bitcoins your cryptocurrency will be stored on whichever service you registered above, however if you want something mobile and want to have control of your own cryptocurrency which you can access on desktop and Android / iOS you should try Exodus Wallet (That is the wallet I use). Exodus is one of the most robust wallet to keep your digital asset safe.
Procedure of sending Bitcoin is very straight forward and simple. Open Exodus Wallet and click on the outgoing arrow, enter the amount in BTC or USD you want to send and paste the Bitcoin Wallet Address. The person to whom you are sending bitcoin will provide you with their wallet address, the procedure is self explanatory but if you want to follow a step by step tutorial please click here.
Receiving Bitcoin in Exodus is very simple and the same procedure applies for almost all Online Crypto Wallets. You share your Bitcoin wallet address and you once bitcoin is sent onto that address you will receive bitcoin inside your wallet. A detailed step by step tutorial can be viewed here.
It's that simple, however if you want to view a detailed guide, you can check out beginners guide to cryptocurrency.
Hope it helps !!!