After you go to the website, wait a few seconds, then look at the upper right of the screen. It will say something like SIGN IN in very tiny letters. It's never there when I first get to the website; it's like it has to pop up.
Not sure if OP is using mobile version but I find that when using a mobile device , the site is very glitchy. The "sign in" is sometimes at the top right as PP mentioned and sometimes you need to find the menu bar/tab to sign in. It can be a tad frustrating because links/tab seem to appear in different places at times - it's like the site is halfway set up to have a mobile version and half is still PC based.