Broken theme-Unable to log in.

Hello.

So basically, I accidentally put something in the function.php section of my coding instead of the footer.php section, I then removed what I put in the function.php section and saved it, however I accidentally removed apart of the function.php coding and now my website has gone down and I am unable to log into it (www.roxi-lola.co.uk) I have read about using FileZilla to fix this, what I gather is that you can edit your website thorugh FileZilla, am I correct? I just need to replace the coding in the function.php section but the thing is, I can’t access my admin panel to do so.

If using FireZilla to do this is correct then how do I find out my username and password? I tried my admin username and password and it didn’t work. The thing is, I didn’t set up my Admin account, someone else did then gave it over to me to build my website so now I am confused to whether there is a different username and password to my admin login.

Help would be greatly appreciated!