If it's for a QT portfolio and you haven't rolled over simply use: @ESZ7 AND @YMZ7 in the symbol column of the Portfolios and Alerts window [go to "Portfolio" and tab to "Edit ...".]
If you wish to trade, I think it depends on your broker. According to IB, which is what I use, for the ES use ESZ7 and for the YM use YM DEC 07 [with a space between YM&DEC and between DEC&07].
lj