The "Tools" section under "Account" provides two HMTL forms you can use to set up on your website to gather email address subscriptions. You may copy and paste this code into your website.
The simple form includes the field for just the email address and the complete form includes all of the available fields for a contact.
On the complete form you may use as many or as few fields as you wish. The only required field is email.
In the complete form you will find a <select> field for the group that includes all of the groups you have created in ResultsMail as options. You may remove some of these options to limit the groups that a contact may subscribe to and in this way use it as a method of segmenting your list.
You may also specify a group in a hidden field by inserting <input type="hidden" name="group" value="Group Name"> where Group Name is replaced with the group you would like to specify for the subscriber. This way you can force subscribers on particular forms into specified groups.
Please see the online documentation located within your ResultsMail account for more detailed instructions.