I have a workflow task that allows a user to enter some info when the workflow is running. These are Task Form Fields. I want to use the information the user enters in these in the task completion step (Create list item) but I am not sure how to access them.
[I edited my answer as I misread your question].
See the steps in this blog post
Basically, you first need to declare a Variable. Then, inside your Task, in Change the behaviour of a single task, you assign the value of your Task Field to this variable and do whatever you need to do with it.
When you edit a task, there is an option "Change the behaviour of the overall task process" and in that "When the Task Process Completes". I guess this is if many tasks exist so doesnt allow access to individual task fields. When using "Change the behaviour of a single task" and in that "When a Task Complete" I can access the current task fields.