First of all, you'll need to create an account at primewin.com — it will take literally a minute.
Then, log in and click the deposit button in the main menu on your mobile device or in the right top corner on your PC.
Alternatively, you can go to the a profile page. There are more useful tools there: you can add another currency, create a withdrawal request, buy crypto with a bank card, and make a deposit as well. You may also check your transactions history.