The courses that you need include in your Personal Study Plan can be chosen from all the courses listed in the curriculum of your degree programme. Please note that some compulsory courses may have pre-requisites (courses which  have to be taken before others). This means that you cannot add certain courses to your APSP without including the pre-requisites first. 
The pre-requisites are listed in the curriculum of your degree programme. Make sure you read it before you make your APSP. 

You can add new courses (belonging to the next academic years) to your APSP,  only after having inserted all your courses belonging to previous years, except for free choice credits.
In  any case, the system running the operations prevents you from making an irregular APSP in which the pre-requisites are not respected. A  warning message tells you  which courses must be included before others.