How to turn on Speaker Phone with Bold 9000?

There are a couple ways.

Easiest is by pressing the dollar key during a call. If you look there should also be a little speaker picture on the dollar key. (I think it was there on Bold 9000, sorry if I'm wrong. It was there on later legacy models.)

There will also be one or two onscreen methods. During a call, is there an image of a speaker on bottom left of screen? If so, does scrolling trackball to left reach it? Try clicking there.
Otherwise, during a call click the MENU key (i.e. BB logo key to right of trackball). From the menu that opens, there should be an option there.