Can anyone help me with this?

What do you mean?

Unfortunately you need to upload the image each time - OR - upload the image and tick the 'public' checkbox, and it will then show up in your templates for you to choose (but will also be public for everyone to see). I need to upload as public because most of the time I am using my phone and imgflip doesn't work with my phone to upload images.

The way I do it:

I save the image on my computer, then when it's time to meme comment, I just click Upload Image and it works fine.

Hope that helps. :)