Resource limitations

I'm looking for a function I cannot find for the life of me:

When assigning resources I sometimes need them to be limited. Let's say I have only 1 person who can do a specific task, and this person is assigned as a resource to 2 tasks. I need the scheduler to realize that this person can only do 1 job at the time, so both activities cannot overlap because this person cannot work 2 shifts a day. Therefore tasks cannot be planned simultaneously but have to end up sequentially after rescheduling.

How can I make this happen?