Details regarding 2019 entry requirements for post/undergraduate courses can be viewed on the online course finder - https://www.qub.ac.uk/study/course-finder/.
If you wish to be considered for an undergraduate course, a formal application should be submitted through UCAS (www.ucas.com). 
In order to be considered for a postgraduate course, you should submit an application through the online application portal - https://dap.qub.ac.uk/portal/user/u_login.php.