If I have open a package in BIDS ("Business Intelligence Development Studio", the tool you use to design the packages), and do not select any item in it, I have a "Properties" pane in the bottom right containing - among others, the MaximumErrorCount
property. If you do not see it, maybe it is minimized and you have to open it (have a look at tabs in the right).
If you cannot find it this way, try the menu: View/Properties Window.
Or try the F4 key.