Font and font size for Welcome to... message

Am trying to adjust the font and size of the greeting Welcome to... at the top center of the center box... (below the Nav breadcrumb, I believe).

I thought I would find it in the stylesheet but have not had any luck.

Can anyone point me in the right direction?

First, you can find more details by view your page sources.
Please find some tools to help yourself and it can save you in finding all the items.
You can refer to some of them in my signature below.

By view the source, and your questions,
There are:

<h2 class='greeting'>
Welcome
<span class='greetUser'>
Guest!
</span>
Would you like to
<a href='http://localhost/zc1301t/index.php?main_page=login'>
log yourself in
</a>
?
</h2>

For the:
Welcome (excluded the Guest!) Would you like to (excluded the log yourself in)?

You can use in CSS are:

greeting {
     font-size: 1em;  /* put the value suite */ 
     ...
     }

For the: Guest!

You can use in CSS are:

greetUser {
     font-size: 1em;  /* put the value suite */ 
     ...
     }

And for the: log yourself in
It depended on the css attribues for the links.

.

Oops!

The above two classes in css should be read as:

.greeting {
     font-size: 1.2em;  /* put the values suite your need */ 
     color: Brown;
     }

.greetUser {
     font-size: 1.2em;  /* put the values suite your need */ 
     color: orange;
     }

Thank you for explaining that and offering your tools of the trade... They should be included in the customizing section as a sticky so everyone is aware of them!