Each form that you create in your AWeber account will have it's own unique "Form ID." This ID is used to track submissions for your forms and to help distinguish your forms from each other in your account.
So for example, in the screenshot below, the "Form ID" helps us to track the 5 submissions to "Form A" as opposed to the 6 submissions in "Form B." Both "Form A" and "Form B" will have separate unique "Form ID's" that help us to track those submissions.
How To Find Your Form ID
If you have not already done so, create a sign up form for your list.
Go to the "Sign Up Forms" page and click the "Publish" link from underneath the title of the form that you are looking to get the "Form ID" for.
Next, you will see the options for how you would like to publish your form. Click on the "I Will Install My Form" option.
So for the below screenshot example, the "Form ID" is 528465752.