I think these are the training times for the Celebrity V5/V5.5; there may be others, but I'm pretty sure these ones will work.
9:30 AM
1:00 PM
4:00 PM
5:30 PM
7:30 PM
Basically, set the time on your Tamagotchi to one minute before any of these times (for example, 9:29 AM, 12:59 PM, etc.) and wait one minute. If then, your Tamagotchi has a speech bubble with an item of some sort in it, you will be able to train it by selecting the Training option (bottom-left corner) and choosing an item for your Tamagotchi to play with.
Sometimes your Tamagotchi will not call for training; this is normal. Just set the clock one minute ahead of the next training time and wait again. ^_^
Training influences which characters you get; see
this chart for more information on the characters available.
This topic will also help you to understand exactly how the bonding process influences the characters you get; it's made for the V5, but most of the aspects apply to the V5.5 too.
I hope I made sense! X3