Pre-populating the promo code for users
The promo code can be pre-populated into the promotion code text box by adding the promo code to the end of the query string used to access the membership form.
For example, if you are sending a targeted email about memberships, you can include a link to the membership form which will pre-populate the promo code and the discount for the user. If the promo code drives a discount, the system will populate it in the box and apply discounts accordingly. If it is a promo code used for tracking purposes only, it will populate the promo code only.
Just add &pc=XXXXX ( XXXX represents the actual promo code) to the end of the long URL (query string) for your membership form, i.e., https://secure.imodules.com/s/153/index.aspx?sid=153&gid=1&pgid=3261&cid=7165&pc=12345. (This is the URL of the actual form page where the user will enter data - the page after they click to make a purchase.)
You can of course make this more user-friendly with "Click here" or other link text, then enter the membership form URL with the promo code as the target.
NOTE: This functionality will not work with the Custom URL in the properties.
Additional Information on URL Customizations: