If you haven't already, please read thru the XLSForm description here, and perhaps take a look at some of the XLSForm intro videos on YouTube, eg Setting Up Your XLSForm or XLSForm 1 Basic Structure for guidance [no association]. You should also read the most excellent XLSForm Tutorial.
Alternatively, you can use one of the existing form builders to create your form; eg KoboToolbox or ODK Build. These will create a valid XLSForm for you, which you can then modify as desired.
Then, if there are specific questions about your particular form that you need help with, please post back and I'm sure someone can help (and if you are getting a particular error, please include that in your description). That, and Google is your friend 