We recommend the Phantom wallet :
Phantom — Crypto & NFT Wallet — Solana | Ethereum | Polygon
For a detailed tutorial, click here.
The best way is with your credit card using Stripe in your Phantom wallet.
You can also buy some with a credit card or a bank transfer from a centralized exchange, like Coinbase, Binance or Swissborg if you have an account there.
Coinbase - Buy and Sell Bitcoin, Ethereum, and more with trust
Invest in crypto assets the smart way⎥ SwissBorg
The procedure should be explained clearly on the centralized exchange you chose.
For an example, this is the tutorial of the Binance platform :