How to allow multiple choices on check box?

I am offering a list of responses.  In many cases, more than one choice is appropriate.

Hi, thank you for contacting us.

I have examined your account and noticed that you managed to create multiple choice checkbox elements already, for example sections "(Optional) Send me information about" and "(Optional) I am checking the aspects of the anti-war movement in which I was primarily involved:".

If you need further assistance please let us know. We will be happy to help. Thank you.