This is the really important bit so taking it from the top...

Fill in your site title and the tagline you want. It defaults to “just another wordpress site” change that so it's not just another wordpress site. You want something that backs up your site title.

So if your site title is

Wealthy Affiliate Review

your tagline could be

A review of wealthy affiliate detailing the good, the bad and a backstage tour

Don't know...

As long as it makes sense and backs up your title.

Remember to set your time zones here as well.