Simply drag the CRX file with your mouse over the Chrome Extensions page... a small "Drop to install" area will appear on the page --> drop the CRX file on it and Chrome will install the extension. It's a standard way to install extensions in Chrome.
I've successfully install spautofill.crx to Chrome Extensions page but still cannot use it on my second Chrome profile. Sticky Password icon is grayed out and clicking on that icon does nothing at all. See attachment.
I'm using latest Chrome (32.0.1700.107) and Sticky Password (18.104.22.168)