The large Object Support checkbox is inside the admin client - choose 'Applications' from the left column, select the Application group you want to update, right-click, choose update, then move to the Load Information tab, it will be right under the tab.
However, before you do that, two things...
Make sure this won't cripple retrieval performance for your users -- large object support is meant for large reports (hundreds to thousands to tens of thousands) of pages. Not using it can cause long delays in retrievals, causing users to complain.
Also, v9.5.0.7 was released last week. Check the wiki for links to FixCentral:
https://cmod.wiki/index.php?title=Main_Page#IBM_CMOD_Fixpacks_.26_Security_Bulletins