Go to your profile by clicking on your name or hovering over your name with your mouse. You will see a link that say "Signature" -> click on the link and just make sure you put the http:// with the rest of the url you want for your signature. See my signature at the end of this post.
Or if you want to put the name of your cattery but make it clickable as a link you would follow the same steps as above, but instead of using a URL, you put put the name of your cattery or cat or whatever you want, highlight it, click on the link icon (on toolbar) and then a dialog box will come up asking for a URL -> type it in and the the name is clickable to whatever website you wish. Or you can even make it clickable to an email address. See my signature for examples. My username can be clicked on so you can email me quickly, the forum name is clickable to the forum and the url for my design website is a url - see how easy
Or if you want to put the name of your cattery but make it clickable as a link you would follow the same steps as above, but instead of using a URL, you put put the name of your cattery or cat or whatever you want, highlight it, click on the link icon (on toolbar) and then a dialog box will come up asking for a URL -> type it in and the the name is clickable to whatever website you wish. Or you can even make it clickable to an email address. See my signature for examples. My username can be clicked on so you can email me quickly, the forum name is clickable to the forum and the url for my design website is a url - see how easy