When you click download link on the download tab this is what you see and should do
Never press download button on the ads!
DO NOT press the ads either.
These possibly could lead you to virus
ONLY press the "Skip" button that is marked.
If nothing happens here, click on the blue link on the page. (you can click on the link just to make it go to next page faster)
Click the Download button.
save where you want it (most likely on the mods folder in .minecraft folder.