Hello and welcome to Sanctum! If you haven't created an account yet, click on the Create Account on the first screen of the game. You will need an account to get an online avatar (the appearance you present to the world of Sanctum). The user name you will use in the game and the house of your starter deck are also determined at this point. If you decide in the future that you don't like your chosen icon, it can be changed with the edit account button.
With your new account, you will have a starter pack of cards configured for the House you choose. Any other cards will have to be purchased at the card store. Each account must purchase its own collection, and no account may use a card that is not in its collection. This may sound self-evident, but consider the case of a user with two accounts. These accounts may not share decks, because they are unlikely to contain the same collections of cards.
Once you have an account, you may enter the Great Hall to look for an opponent. There are two realms for Sanctum play: the Plains of Grace, the default realm when you log on, and the Dueling Grounds, which may be reached by clicking on the pull-down icon next to the realm box in the upper left hand corner of the screen.
The Dueling Grounds are intended for people who already have at least one booster pack, and it is recommended that you not enter the Dueling Grounds until you are reasonably confident about your deck's ability to compete with people who very well may have access to every card in the game. Ranked players' games in the Dueling Grounds will affect their ranking, while games in the Plains of Grace do not affect ranking, so that the big dogs can't enter the Plains of Grace to pick on new players just to drive up their ranking.
To see how another player is ranked, click on the avatar you want to examine. You will see how many games they've won and lost, as well as their ranking for the realm and percentage of games completed.
Now, you're in the Great Hall, and there will be avatar icons (including yours) in the large window to the left of the screen, and conversation scrolling peacefully along in the right-hand window. Chat may be entered in the box in the lower right. Press enter and the chat will be transferred to the scrolling conversation. If you want to talk more privately, click on the avatar of the person you want to talk to, and mark the "whisper to" box below the chat window. The dialog you type will show up on your screen with the word whispers.
For instance "Caliban whispers: Hey, Stephano. Want to play?" Only Caliban and Stephano will see this dialogue.
From this screen a challenge may be issued by clicking on the icon of the avatar you wish to challenge, and then clicking the challenge button in the lower left hand corner of the screen. Alternately, simply double-clicking on any avatar will bring up the challenge option.
Note that you can not challenge a player if you are currently being challenged yourself. Also, if you challenge someone who is currently involved in another challenge, the game will open a dialog window with a message to that effect.