How do you assign the same task in 2 different projects?
Hi @Ann_Ruckdaschel , welcome to the forum 
A task can be multi-homed (not assigned) to several projects, meaning the same task (not a duplicate) can appear in more than one Project (in either List, Board, Timeline, Calendar views).
You can easily multi-home tasks by going into the Task’s details pane, look below the Assignee and Due date you will find ‘Projects’ and ‘Add to projects’. Once you click that, you simply type in the name of the project or select one from the list that Asana thinks you want to add the task to.
You can read more on this in the Asana guide here
Thank you. The project isn’t showing up when I go to “add project.”
Yes I did.
If the project is not showing up, then it may mean that you cannot see it, i.e. it is private and has not been shared with you. Check with the project owner and make sure they add you to the project.
If the problem persists then please upload a screenshot, if possible (hiding any personal information).