Did you notice that Google recently upgraded their AdWords interface?
They moved the Keyword Planner, so if you're looking for the Keyword Planner tool, here's where you can find it:
In upper right, look for the Menu - it looks like three vertical dots
Click on the Menu dots to expand the menu.
Under Planning on the left of the menu, find "Keyword Planner".
Now get to researching those keywords! :)