To buy or sell a token, click 'Trade.'
Choose 'Pay with Crypto' or 'Pay with Credit Card.' (If paying with Credit Card, follow the instructions provided to create your Portis account. Portis is a crypto wallet with email and password login, like any other website. Portis is your friend.)
Use the dropdown menu to choose a payment currency. (If paying with a Credit Card, choose DAI to save a few dollars.)
Enter the desired purchase amount.
Locking tokens means you will be unable to sell or withdraw these tokens until after a certain amount of time passes.
Why lock tokens?
Lock tokens to show your confidence in the long-term value of a listing. The lock assures potential buyers you won't sell as soon as they buy in after you, and the confidence it takes to lock tokens creates "market signal" — it makes the listing more attractive.