How do you make a jpeg file smaller?

[my2leftfeet]

Trying to get online invitations printed and falling at the first hurdle. I have a jpeg of company logo that apparently is too big - can anyone give me "clear instructions" as to how I can make it smaller. I'm pretty useless at this type of stuff!

 

[z107]

What graphics software and computer do you have?
(Photoshop, paint shop pro, mac/pc.)

 

[DrMoriarty]

Picasa is free to download, and very user-friendly despite all its features (including a one-click 'resize' function)...