External HD from my PC wont work on my mac, yay!

So I have an external hard drive that I used to back up all my files that were on my pc. Now when I plug it into my macbook I can only read. I need to be able to write too… anyone know what the problem might be? I can’t change it for some reason. On my pc it is read/write.

woooo weee yeah wahhh yeeess!