If you are looking for a module that you can't see on your Dashboard, you can try to find it via the COURSE SEARCH box. It is located in a 'block' in the right column of the Dashboard page. Moodle uses the term 'course search' rather than 'module search'.
Please note that module leaders release their modules to students at the beginning of the semester. You cannot see any modules which have not been released yet. If pre-reading is being offered (or required) modules might already be released before the start of the semester. This depends on the module team. If you find you cannot see a module which you think should be available to you please do contact the module leader.