How to ensure images whic are Copyright-free and Royalty-free are accepted by Google Play

I’m trying to upload an AI2 App to Google Play, to raise money for a charity. The App will be free, with a link to JustGiving.
I’ve completed all the requirements on the Google Play desktop (all green ticks) but I don’t know where/how to tell Google Play that all the images used are free of copyright and royalty.

I could supply them with a link to the website the images came from, or a cut-and-paste of the conditions which confirms this.

I hope this is posted in the correct place. Any questions (or preferably solutions) would be very much appreciated.

According to intellectual property section of the developer policies, if you have written documentation proving that you have permission to use the material you can submit it in advance.

Thanks for your reply.

All I have been able to learn from the intellectual property section is how to complain when I think copyright has been ignored.

I guess I must be missing (or misunderstanding) something in there.

Could you, please, hand-hold me to the relevant info?