Put you page or post in “Text” view to reveal the html code. You should see something like:
[su_tabs active=”3″]
[su_tab title=”Title 1″]Content 1[/su_tab]
[su_tab title=”Title 2″]Content 2[/su_tab]
[su_tab title=”Title 3″]Content 3[/su_tab]
[/su_tabs]
Tabs (with an “s”) is like a container for the all the tabs you want. Tab (without an “s”) goes between [su_tabs] and [/su_tabs]. I’ve displayed an example above. (Note this is with Settings => Compatibility Mode box checked which turns on the “su_” prefix).
In the [su_tabs] shortcode there is a parameter that says ‘active=”3″‘. This controls which tab is presented when first opening the page. If you don’t put any parameter, it should default to the first tab. In the example I’ve shown, it should open in tab 3.