I've recently opened a Bitcoin account
Where did you open the account?
Different services have different user interfaces. Without knowing which service you are using, it is impossible to explain how to use that service.
and also opened a wallet through the site.
Do you have an account with a service, or a wallet that you run on your computer? Which wallet are you using? Different wallets have different user interfaces. Without knowing which wallet you are using, it is impossible to explain how to use that wallet.
I'm trying to learn about how things work, and when I click on "Buy Bitcoin" I am prompted to enter my Bitcoin address. I don't know what my Bitcoin address is or how to find out - can someone enlighten me, please ?
If you have a bitcoin wallet, then the wallet should provide you with a way to see a receiving address for that wallet. achow101 has already provided basic instructions for finding the address. If you provide us with more information about your choices, it will be easier for us to provide you with more specific instructions about how to use your wallet.
