www.wysiwygwebbuilder.com

Is there a way to install a new font ?
I have downloaded the Philosopher font and would like to add it.

You will need to install the font on your computer and then load WB. This way the program will show the font in the list and be usable in the program. You will need to go to options and fonts and add manual @font-face information so that the correct code is added to your webpage for it to show.

I have downloaded the Philosopher font and would like to add it.

Isn't Philosopher an Adobe font? Not sure you can install it directly into windows for use. See the following from Adobe
Philosopher
Using Adobe Fonts in Creative Cloud apps