A default Mantis settings form have 7  pre-entered fields:project_id (required) : Id of project for which issue is bieng created.To get project_id open /bug_report_page.php page and view page source.

search for “project_id” in page soure, value attributes of option tag which follows select tag having name attribute equal to “project_id” are id of projects.

category_id (required) : Id of category to which issue should belong. Search for select box with attribute name equal to “category_id”, value attribute of options tag of this
select tag are id’s of category which can be used here.

reproducibility : Similarly like above fields search for select with name attribute equal to “reproducibility” and select values from the option tag.

severity : Search for select with name attribute equal to “severity” and select values from the option tag.

priority : Search for select with name attribute equal to “priority” and select values from the option tag.

handler_id : User id to whom issue should get assigned. Search for select with name attribute equal to “reproducibility” and select values from the option tag.

view_state : Search for input tag with name equal to “view_state” and enter value attribute information of the view_state.

Setting up custom Mantis Fields

For adding a custom field, Field input of the form should contain id of the custom field and value the value you want to send.
Field name should be like “custom_field_<custom_field_id>” for example custom_field_2.
In order to know id of custom field, open /manage_custom_field_page.php, field_id present in get string of their view url is their id.