CINAHL's options for limits can be found in 3 places
The Edit link in Search History [all options]
Using the Edit link on a line of the search history opens the full array of possible limits. It also gives the option to change your search string if, for example, you used an AND where you should have used an OR. Selecting options here and saving clicking Save at the bottom will update the search in your history.
The Advanced Search link under the search boxes [all options]
Using Advanced Search opens the full array of possible limits. If you do not enter text into the search fields, then when you hit search it will apply the limits to the last search in your history which does not already have limits applied.
The left-hand Refine Results pane [few options]
Using the Refine Results pane, you will see only seven of the more common possible limiters, along with two database filters.