Go to the Poloniex website homepage, and click [Buy Crypto] on the top navigation bar. If you are using Poloniex App, tap [Buy Crypto], then you will land on the page for crypto purchases.
Choose the [Buy with Fiat] tab. Select the fiat currency you'd like to buy with and the asset you'd like to buy, then enter the asset amount.
Select your payment method. Please note that the fees and payment process vary with your choice of a third-party service provider. Please select the one that works best for you.
Confirm your transaction, then you will be redirected to the third-party service provider's website. Please follow their instructions to complete the purchase.
If the purchase is successful, you will see a record in the [History] tab, or you can check the details in your [Wallet].