You'll definitely be able to easily link directly to one of your signup forms in your mailing:
Head to the Audience page of your account, and scroll to the bottom to locate your Signup Forms. Click the "Classic forms" tab.
Locate the form you'd like to link to and use the dropdown menu to the right to select "Add this to your site".
Now you'll see a new window with the various publishing options for the form- you want the top entry: "Link to it"
Copy the URL in the "Link to it" field. (I like to go ahead an paste that URL into a text document to make sure I have it handy when I navigate away from the window)
Now, you'll have that URL copied and you can paste it into your personal email (or link behind text) as needed. You can use it create a link in an Emma mailing as well- you can even create a button in your next campaign that links directly to your form!
I hope this helps- please don't hesitate to let me know if you have any other questions!