If you have Java 1.3 or above, FoundationStone can load the fonts it needs automatically. However, if you install them in the usual way you can use them in other programs. It is recommended to use the edit menu's "copy as Unicode" feature to exchange Hebrew text with outside programs - FoundationHebrew uses a non standard encoding, so using it outside FoundationStone is discouraged.
You will find two Hebrew Fonts as part of the download (in the "Fonts" directory). FoundationHebrew (Founhebr.ttf), the default printed script, and FoundationHebrewScript (Founhebs.ttf), a cursive script.
Install the fonts using the "Fonts" control panel.
You can do this from the "Start" menu on the bottom left of the Windows screen - go "Settings" then "Control Panel". Double click on "Fonts". Pull down the "File" menu and choose "Install New Font...". You then need to navigate to C:/Program Files/FoundationStone 2.3/Fonts/, then press buttons "Select All" then "OK". Note that exactly how you install fonts varies slightly between versions of Windows.