Up the top right is 3 horizontal lines. Click on that, then select settings. Scroll down to the bottom and select show advanced settings.
Under the Privacy heading, click on the Clear Browsing Data button. In the popup box, tick the options you want to delete. If the top dropdown box doesn't say Obliterate the following items from the beginning of time, change it to that.
Be aware if you tick the password box, you will lose all your saved passwords. I would suggest only ticking the cookies and cache option, but you can select the top 2 as well if you're not worried about losing browsing history.
Last thing, click the clear browsing data button. I always find it helps if you reboot after doing this, but I don't know for sure if it's required or not. I just figure it can't hurt.
