If you wish to you can use your own HTML signup form. To do this navigate in the merchant panel to Configuration > Affiliate signup > HTML form (tab). There you can download a raw html code of the signup form.
The code gives you a basic idea of how the signup form should look like. You can customize the form the way you need, but you have to keep the given input field names.
Actually, the HTML form inherits  the field settings applied at Configuration > Affiliate Signup > Fields (tab).
You can find more info about html signup form here:
http://demo.postaffiliatepro.com/samples_tests/signup_html.php

 

Payout options are not displayed in HTML sign up form

The signup form code does not include payout options, so if you want to manually add it there, you have to find out what IDs are assigned to each payout option and add the code manually.

How to do that?
In the merchant panel navigate to Configuration > Payout Options here you can see all your defined payout options with its ID (Payout Option ID).

If you know that all affiliates registered via your HTML signup form should use only one certain payout option you can use ID as hidden input field. For example PayPal:

<input type="hidden" value="8444af30" name="payoutoptionid" />

Otherwise you could create listbox with possible options.

Then you have to define input field(s) for each of the field of the particular payout option. For example PayPal has only one field for PayPal email address, its code is "pp_email", input field will look so:

<input name="pp_email" type="text">

For each payout method you can see payout option fields names in edit section (pencil icon) of payout option, scroll to Fields table. Example for PayPal:

If you want to let to choose from more payout options, you need to create some logic for displaying particular fields from chosen payout option, or you can display all fields from all payout options (only fields values for chosen payout option will be saved).

 

Further customization possibilities:

1. Assign affiliate to campaign at signup
- activate plugin
Signup affiliate automatically to campaign
- add an input field with name a_cid to your signup form. This field must contain id of the campaign to which the new affiliate will be signed up.
 
If you wish to use a custom login form, check it out here: