Problem transfer Apps from Itunes to Iphone

Hi
I download from the App store 2 applications to my Imac itunes .
I plag my Iphone in and press Iphone on the Itunes library ,
when I press the Tab Apps - so screen is frozen ..on right side
under SYNC APPS I see only the 2 new apps I bought
and on the right side theres pic of the Iphone Icons presentation
, but it doesnt give me the option to drag / add new apps
it only give me the option to press SYNC APPS and it warn me that
if I do so all apps on my Iphone will be replaced with apps on my library ...
so what should I do if I dont want to replace my Apps on the Iphone and just manually add the 2 new Apps I just downloaded ?
MAC iPhone OS 3.1.3