CSS Help please


New Member
I've just updated to the latest version which has a whole new look and new CSS.
In my previous version I amended the CSS to get our company logo appearing in the top left box where it now says name of the account and the mailwizz logo.

I've uploaded a logo in customization and also tried to amend the CSS as I did it before but neither is working.

Any hints tips as to how I can get the full box top left of customer/backend screen to display our logo?

Thanks in advance.
Can you let me know which file this is in and the best way to form it as everything I try doesn't display!?
Thanks again.
@DasGoot - Sure, here's the css, you can create a file named style-custom.css in /customer/assets/css folder and put below in it:
.main-sidebar .user-panel { 
   background: url('https://placeholdit.imgix.net/~text?txtsize=18&txt=mailwizz+is+awesome&w=200&h=50&txttrack=0'); 
   height: 50px;

.main-sidebar .user-panel .pull-left { 
The result:
Screenshot 2017-03-14 11.56.47.png