To add a form in the menu editor follow the below steps:

Step 1: Login into Mobiconnect with Owner/Admin credential and select your project.

https://www.mobiconnect.net/login

Step 2: Navigate to the Menu Editor page by clicking on the menu editor menu.

Step 3: Select the user from  Select Menu the drop-down.

Step 4: Click on the Forms icon.

Step 5: If there are no forms created for the project then you can create them by clicking on forms, it will navigate you to the form builder page.

If you need help creating a form, please use this link to Create a new form. How to publish a new Form. 
or
If the forms are present, add a form in the menu by drag and drop or by clicking on the "+" icon.

Step 6: Click on the Save button.

After saving the form as a menu, you can access created form directly by clicking on the Form menu.