How to buy coins

I looooved this app and used it often but now with the coins that is says I need to buy, I cant get it to work!!.. How do I buy coins?? I am willing to in order to make the video but how??.. If anyone knows please tell me!!

Clutch player 1000 about PicSlide slideshow maker - stitch photos and music together to create an awesome video picflow and share it on Instagram, v1.0.2