After submitting your form, you can redirect your users to a different website by setting a specific URL or just simply show your gratitude with a 'Thank you' message.
For that go to your Boom Form Settings>'Action' section> Actions After Submission.
'Thank you' message.
From the Dropdown menu of the Actions tab, select show 'Thank you' text.You can customize and change the content of the 'Thank you' text.
For that go to the Settings > Main > Confirmation message and write a text you want to be popped up after your users submit the form.
Redirect to URL:
Simply choose the 'Redirect to URL' option and place a link on the corresponding placeholder.
Also, pick if you want the redirection process to take place at the Same or New tab.
Note
Set the Form state by Showing/Hiding/Locking it, after submission.