You can upload a company logo to your website and it will automatically populate the appropriate places. The process is the nearly same for uploading a brand new one or replacing an existing one. Here are the steps:
STEP 1: Log into your website dashboard (if you don't know how to do this, click here). Once you're in, click on the Design tab, then click on the Logo tab.
STEP 2: If you already had an existing logo, you will first have to remove it by clicking the Remove button.
You will now see the option to upload a new logo. If you didn't have a logo in the first place, you'll already be here. Click the Choose File button.
You'll see your computer's file browser appear. Navigate to the file and double-click on it to open it. You'll see the file's name next to the Choose File button. Click the Upload button underneath.
Now you'll see the logo as it's going to display on your website. Finally, clive the Save button at the top right for the changes to take effect.
If you have any more questions, feel free to submit a support request here.