[Archemedia]

I'd like to have some advice on how to achieve the following:

In a simple project, there are 2 tasks, each taking 3 days of work.
There is only 1 resource, which is assigned to the 2 tasks.

After assigning, the resource is overallocated (200%) so I have to level the project.

The result is that the first task in my list will be handled before the second task giving my resource 6 days of work. The first 3 days on task #1 and the following 3 days on task #2

My question:
How can I obtain that my resource will work on BOTH tasks for 50% during 6 days?