Instagram is a little tricky. You can't post links in your posts on Instagram.
So, take a screen shot of your campaign to post to Instagram (with a description about what you're raising money for, and don't forget the hashtags!). Also, in the description, let your readers know that you're posting a link to the campaign in your profile.
Now, once you've posted the picture, add a link to the campaign in your profile section.
That's it...you just posted the campaign to Instagram!