For an approval to work, it has to be dependant on previous tasks... otherwise it's not an approval task.  There is a section called "Tasks to approve" that replaces the usual "Depends upon" -- and in there you just tick which previous tasks you're going to be approving.  

For example, in my VAT return workflow, I've added a step to approve the VAT return once it's prepared: 

For each box you tick, you get an approve / reject button in the actual job, like this: 

You have to approve / reject the prior tasks before you can complete the approval task and move on.  

If you don't have any tasks ticked in the "Tasks to approve" section in the workflow, then your approval task won't be doing any approving -- you'll be able to complete the approval task without approving / rejecting anything: