If I understand your question correctly, you need to put the old key in the "I" position to be able to press the pin down to remove the old cylinder. Try it on your new one to see how much more the pin moves when in this position.
To install the new cylinder, put turn the key almost to the "I" position, slide the new cylinder in until it stops, and then simultaneously push it in and turn the key all the way to the "I" position. It should slide right in.
1993 Accord 2.2L EX, AT, 94K