You can edit the logo-landing2.png from the folder app\img-assets. Also, if you open each page, you will see the tag inside <header>:

 <div class="logo-container">
  <div class="site-logo">
   <a href="index.html" class="site-logo-anch">
    <img class="logo-img-sticky site-logo-img-sticky" src="img-assets/logo-landing2.png" alt="logo" title="membership">
    <img class="logo-img site-logo-img" src="img-assets/logo-landing2.png" alt="logo" title="membership" width="196" height="36">
   </a>
 </div>
</div>

Here you can upload a different image for the sticky logo.