For submitting custom post type, you need to create a form, and then use the form in a page. What makes it different is that, you need plugins like woocommerce which will have it's own post type like product. How to submit a post using custom post type is described in a few steps below:
step 1: Creating a form
Navigate through WP User Frontend > Post Forms > Add New. Create your form with necessary form fields. Save the form.
step 2: Setting Post Status
Next you have to navigate through WP User Frontend > Post Forms. Edit the existing form by selecting Settings > Post Settings > Post Status. You will see your custom post types available there. Select your post type and save the form. Check out the screenshot below:
step 3: Creating Taxonomy
Next you have to go back to Form Editor and then under the taxonomy section, you will see custom taxonomy, for Woocommerce there will be product categories, product tags. Save the form.
step 4 : Create the Page
Next copy the shortcode of your form and then create a new page or edit an existing one. Paste the shortcode. View the page in the browser.
Your custom post type submission is complete.