I am new and just starting- I am wanting additional fonts to do a cake topper- how do I install fonts to inkscape?

Add it to your fonts on your pc. Restart Inkscape and it should show up.

You need to install your font for all users. Once you have the font downloaded and extracted, right click on the font you want to install and a dropdown menu will appear. Click on 
"Install for all users". Do close and restart Inkscape if it was open