If you're wanting to make a gif check out this link. (http://picasion.com/)
When adding a gif to your signature all you need to do is go to Profile >> Forum Profile Information and then go to the signature section and enter the URL to your gif in between this code: (http://URL GOES HERE)
Then save your details and done c:
Here floof, here's also a proper way to install Signatures
Ok so first you are going to need to go to a image sharing website such as tinyurl.com or photobucket. Ill use photobucket as a example since I use this often
(http://i1299.photobucket.com/albums/ag69/Youshallfearme2/be5a907e-b1f2-46bc-8ed6-21ef6ea30650_zps7aa4084c.jpg)
Click into photobucket and search up the image you are wanting.
(http://i1299.photobucket.com/albums/ag69/Youshallfearme2/9c16d016-f80b-457f-929f-281c69c4e112_zpsa695426d.jpg)
Once you find your image then your screen should look more or less like this. On the right hand side gives you coding so this certain image can be viewable on other websites
(http://i1299.photobucket.com/albums/ag69/Youshallfearme2/19fb9805-b00e-44f0-bd5c-600a6577b899_zps5dda90a5.jpg)
from there all you need to do is copy this coding only in the IMG section found on your right hand side of photobucket. After that you need to shuffle back to Feral Heart and go into your profile and click on Forum Profile Edit
(http://i1299.photobucket.com/albums/ag69/Youshallfearme2/2f2888e5-1467-46e5-9799-62d03fb6bf12_zps392e675d.jpg)
After you click that then it will give you options such as "Signature" which is what you want. From there you just input the IMG coding you have gotten and then save it. In a few minutes or so you will have a signature.
(http://i1299.photobucket.com/albums/ag69/Youshallfearme2/a5d97274-8dec-4bb4-8654-145472751911_zps977f883b.jpg)
Again I do hope this visual representation helps you in some way. It's the basic general form of putting images on feral heart and just a reminder that there is a limit size to what signature you are able to put in.
Good luck