The requirements depend on the university you choose, because each university has its own admission requirements for its Developmental Studies programs.

It also depends on where you want to study. If you plan to continue your studies in the US, you must take a TOEFL test. Similarly, for UK, you must take an IELTS test. These two tests may be required to show your proficiency in English language for other countries too. Besides, you may also need to take a GRE test.

For admission in a graduate level, you obviously should complete a bachelors/undergraduate level. As you want to get admission in a Developmental Studies, and as it considered one of the Arts programs, you may qualify if you have a bachelor’s degree in any Science major.

I’m not sure if your Diploma in Accountancy and Certificate in Procurement will qualify you for admission in Master’s in Developmental Studies program, but, as you’ve said that you have a degree in Developmental Studies from Mbarara University, is that degree a Bachelor’s degree? If yes, you definitely qualify for admission.