Right-click the downloaded .ttf file and select "Install." Alternatively, drag and drop the file into C:\Windows\Fonts .
Some applications (like old versions of Adobe Illustrator) do not recognize font weights properly. They rely on the "Style" flag inside the font file. Solution: Do not use the "B" (Bold) button in your toolbar. Instead, manually select "Sutonnyomj Bold" from the dropdown font menu. If that fails, try downloading a different version of the font from another trusted source.
Web usage (self-hosting)
The variant provides: