Step 1: 

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. 

Step 2: 

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. 

Step 3: 

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. 

Step 4: 

Confirm your transaction, then you will be redirected to the third-party service provider's website. Please follow their instructions to complete the purchase. 

Step 5: 

If the purchase is successful, you will see a record in the [History] tab, or you can check the details in your [Wallet].