Maybe a little more detail would help us answer? In general though select
the object to animate and choose custom animation ( in 2007 Animation Tab in
2002/3 it's in the Slide Show menu)

Select Add Effect and add the required effect

Regards John

Apply "Slide show / custom animation"? What do you want to do? And which
version of Powerpoint do you use?

What John and Pia said. Also, have a look at bettersolutions for more
explanations:
http://www.bettersolutions.com/powerpoint/PCO118/YI911610888.htm

Microsoft provide 3 free training courses on animations. See here:
http://office.microsoft.com/en-us/training/CR061832731033.aspx

Lucy