Help needed. Moesia theme, changing images

Hi

I need some help please. I am a very new user of wordpress and am updating my website myself. icubedhomecinema.co.uk. My site is currently running a holding page

I have got to grips with most things but using the customiser sections, but I can’t change any images or upload logos etc. Have also tried on each page to add logo and images but no go.

Will need a guiding hand please.