You must use the assignments that OCR have provided for the internally assessed units.
The set assignments set the scenario, are task based and the tasks tell you which LO (Learning Outcome) they apply to.
Although you cannot create your own assignment you can make modifications, these are called permitted changes. This means you can for example put the scenario into a local context as a focus or you could change who the individual is and their needs. However, you must not change the learning outcomes, marking criteria or supervision requirements. You should also note that if the task asks for two of something e.g. two plans, then two plans must be produced. You cannot combine them.
You can find the information on permitted changes in Section 5: Scope of permitted OCR-set assignment modification each of the set assignments