Grab image on page from admin image picker

I am trying to grab the image from this admin form field and place it on the page through the template. I have tried many different examples and nothing works. Can anyone point me in the right direction?

            type: filepicker
            folder: 'theme@:/images'
            label: Select a file
            preview_images: true
             - .png
             - .jpg

If the field is already saving to the page header, you just need to use {{ header.chooseimage }} in your page Twig template to render it.

Thanks for your help, I eventually worked it out as I was pulling through content in the same way. I still struggle with the media, but I guess I just need to work out the syntax as I am new to Grav.

Thanks for your help.