If you're talking about in admin panel the easiest way is to replace the current logo image with you're new one, just ensure it's a png image and entitled logo. After moving Ctrl F5 and it will show.
administrator/templates/rt_missioncontrol_j15/images/logo.png
May need some css customisation if the size position is different in which case the section you're after is:
administrator/templates/rt_missioncontrol_j15/css/core.css Line 136
Modify as required:
#mc-logo {padding:10px 0;overflow:hidden;}
#mc-logo img {margin:0;float:left;}