Pinterest images - help

Hi there BHW members , can I ask you where can I get or download images for pinterest for weight loss , fitness niche . I see all those nice images with typography on pinterest - like some fit lady with tipography all over the image : 5 tips for how to lose weight. Where can I find that or can I just download that image and use it on my website/blog for free if Im in affiliate marketing .

and yes Im newbie

Thanks in advance