Site Title Customization

That is completely dependant upon your current theme.

Hi Esmi, the theme is Twenty Eleven

You will need to start customising your theme but do not edit the Twenty Eleven theme. It is the default WordPress theme and having access to an unedited version of the theme is vital when dealing with a range of site issues. First create a child theme for your changes.

OK, after I have created a child theme for my changes, what is the next step please?