Just a few other tips - to add the font to the Fonts directory in Sigil, click the right mouse button on the Fonts folder in the left panel and pick "Add existing item..." Then browse to the font and pick it. It will be added to the epub archive.
As far as where to put the font specification in the style sheet, I think I'd put it right at the top.
@font-face {font-family: "name"; src: url('..fonts/name.ttp'); }
Then use it for the body tag:
body {font-family: "name" }
I have not tried this or tested it, but I think you get the idea.
Use forward slashes, by the way. Backslashes is a WIndows thing).
Let me know if this helps, please.
Edit - took out the last line, which was in the wrong place and leftover from an ealier attempt...