Mouse exclusive to my game

How do I make the mouse exclusive to the game? I am new to all this and still in school, but I cannot figure out how to make it so when you play the game the cursor goes away. We use dual monitors here and if I keep trying to look right the mouse goes off the screen onto the other monitor. It would be much appreciated if someone could help out.

Thank you.

Take a look at Screen.lockCursor.

Updated to highlight web-player-specific behaviour:

In the web player the cursor may only only be locked after the user has clicked on the content and the user has not left the content view with the cursor. After the user presses escape or switches to another application the cursor will be automatically unlocked. The cursor lock will also be lost when exiting full screen mode. You can query if the cursor is currently locked by checking the lockCursor state. To provide a good user experience it is recommended to only lock the cursor as a result of pressing a button. Also you should check if the cursor got unlocked, in order to e.g. pause the game or bring up a game menu. In the Web Player and Editor the cursor will automatically be unlocked when you press escape. In the Standalone Player you have full control over mouse locking thus it won't automatically lose mouse lock unless you switch applications.