To see who last visited your profile, just select "Profile Visitors" on your overview page.
Alternatively, select "Matches", and then "Profile Visitors" from the menu on the left. Here you can see when each match in this list last visited your profile.
You can also select "Last viewed" to see those profiles you last visited. The date you last visited this profile will also be displayed.
If you're on a mobile device, you will be able to find "Profile Visitors" and "Last Viewed" in the menu under "Matches", or at the top of the screen if you're already on "Matches".