Apple Mail Signature Problems

I want to use Apple Mail instead of Gmail, but cannot create a signature in Apple Mail. In Gmail, I currently have some images, text, and hyperlinks laid out nicely as my signature. When I copy-paste the signature into Apple Mail, the formatting is lost, the image becomes gigantic, and everything looks bad. I'm unable to alter anything in the settings, and have no idea how to fix this.

Here are two images-- the first is the signature as it looks in Gmail, and should look in Apple Mail. The second is how it actually looks in Apple Mail.

I find if I go to Gmail, compose a new message, copy the signature, then paste it into an email I'm composing on Apple Mail it looks fine, but that is a ridiculous, time-consuming thing to have to do every time I write an email.