To find any of the descriptive statistics, go to the "Stat" pull down menu and select, "Basic Statistics", and then "Display Descriptive Statistics". The following screen will appear.

I have called my data, octane ratings. In order to get descriptive statistics on it, double click on C1. You can type it in, but you have to type it exactly as it appears in the grey box for each column with the single quotes. Hit ok. This will be your output.
 

Descriptive Statistics: octane ratings
 

Variable             N       Mean     Median     TrMean      StDev    SE Mean
octane r            79     90.557     90.400     90.530      2.650      0.298

Variable       Minimum    Maximum         Q1         Q3
octane r        83.400    100.300     88.700     92.200

N is the number in the sample, Mean is the sample mean, Median is the sample median, TRMean will probably not use, StDev is the standard deviation of the mean, SE Mean we will cover later in the class, Minimium is the sample minimium, Maximium is the sample Maximum, Q1 is the first quartile and Q3 is the third quartile. If you computed Q1 or Q3 by hand, you may get slightly different numbers.