Your hosting is managed in the DirectAdmin panel. The easiest way in is from the client area:
You can also sign in directly. The server address (e.g. zeus.boost.pl) and your username are on the service page under Server information. Open the server address with port 2222 in your browser, e.g. https://zeus.boost.pl:2222, and sign in with your hosting username and password.

DirectAdmin speaks several languages. Press the language button (e.g. PL) in the top bar and pick English; the panel remembers your choice.
The right-hand column shows your plan's limits and how much of each you use: disk space, bandwidth, mailboxes, FTP accounts and databases.