Edit "[sitename] Blog" top of Theme's Blog Page

So at the top of my theme's blog page, it says "[sitename] Blog", except that [sitename] represents my site's name. You can see exactly what I'm saying from the screenshot attached (it's like a header or something, where the page's name in WordPress goes in my theme).

I want to change that text to something else instead of "[sitename] Blog"... Would someone provide instructions on how to do this? If any more details/information is required, just ask. I will not provide URLs or credentials on the thread though... if a staff members requires these to investigate, please provide instructions of how you want them to be sent via the WPMU Dev contact form and what exactly you would like sent.

Please respond ASAP. Thanks in advance!