Unless an application already has the font available for installation (Fontomizer, Font Installer, etc), you will need to root your phone in order to remove the warranty.
In case your phone is already rooted, simply connect the phone to the computer and copy the fonts to your storage device(internal/external). Then use a file explorer(Root Explorer, Astro File Manager) and copy the fonts to /system/fonts folder and perform a reboot of your phone.
After the phone has restarted, use the main menu > Settins > Display > Fonts and choose the corresponding font you want to use.
