You have a free hosting from Bravenet so you will need to use a hosted email form provider. Bravenet are one of many firms that provide this service. You are not obliged to use Bravenet services just because your site is hosted here.
Most form services provide an on-line builder so that you do not need to understand the underlying html. Use this and then follow the instructions in the Copy/Paste forum for inserting the generated code into your web page.
You must copy ALL the code. Do not try to make changes to the generated code, that is what causes many forms to fail.
If you still have a problem then you need to give us full details.