I got a vector arrow from the website shown below.
I edited the arrows colour in Illustrator. I saved it as a .png file.
I went into Muse and clicked File > Place.
I navigated to where I had saved the file. I clicked Open.
I positioned it on the page. I clicked the anchor button. I clicked at the top of the canvas to place the anchor.
I clicked on the arrow and then I clicked on the drop down menu. I selected ‘top’.
I edited the scroll settings.
I uploaded the changes to the host and checked that it worked.