Splash Image

How do I change the Splash image?

I know to go to Admin>Basic Settings>Splash.  I see the "Insert/Edit Image" button, but I do not see a way to upload the image.  I do not have a URL for the image either because it is on my computer and I can't seem to figure out which folder I would need to upload the image.

Could someone share with me (in very basic terms) a link to the steps of where I would need to upload the image in the cPanel or Admin side?

Splash image location /templates/base/images/bx_splash_image.jpg

Orig.size;     1120px × 240px

So I upload the image file in the "/templates/base/images" folder on the server. 

Do I need to name the image "bx_splash_image.jpg" or can it be called something else?  I ask because I wondered if naming the image something relevant to the keywords of my site would be helpful with SEO.

 You can name it however you like but you will need to change it in the common.css for the base template. You should also be able to go to Admin>Basic Settings>Splash and click on the "HTML" icon and update the file name in the HTML code there.

Really Confusing on my old site I can just insert the image and have no problems.