The summary is usually what shows when viewers find you in the search engines.
If you don't know where to find the Summary: Go to a Hub, then to 'Edit' in that hub.
Over on the right hand side of the page you will see the third grey box down has a tab called 'Summary' open that up and a blank text box will open for you to enter your 'Summary' I would suggest while you are there check out the Tags etc. When you are happy just click 'Done Editing' up the top of the page :-)
Good luck :-)