For those who are lazy, you can always find most commands in the Insert menu given you're in the right workbench.
In the View menu>Toolbars, you can enable any of the listed ones. Always keep it to a minimum so that you don't clutter your user interface.
If all fails, go to Tools>Customize, Toolbars Tab. then click Restore Position button. This will bring CATIA back to the original factory UI settings.
For those who would like a reference page of most icons in their respective workbenches, I've uploaded a copy of icon screen shots. Click here to download.