Hi.  It isnt hard to teach a dog to use pet steps, but it may take a little time.  First get some treats - really yummy ones like cut up hot dog pieces.  Then:

1) put a treat on the first step, and let your dog walk over and eat it.  Remember to say "good step" while your dog is eating the treat off of the step. 

2) Then put your dog's paw, or whole body (if it is a small dog) on the first step and say "good step" and give your dog a few treats (this is called "jackpotting").  Let your dog jump off the step. repeat this a few times

3) repeat the first step (treat on the first step) and then add another treat a little out of reach so that your dog has to put his/her paw on the step to get it.  Remember to praise your dog like crazy when he/she steps on the pet step.  "good step! good step!"

4) Slowly add treats a little out of reach so that your dog eventually climbs up on his/her own! 

The most important things are to give treats whenever your dog is on the step, and to praise your dog a lot for being on the step.  Once he/she sees that the stairs are not scary, but are actually a good thing, then you will be able to stop giving treats.  It may take a few weeks to get your dog totally comfortable with the steps, but after that you will be suprised you ever lived without them!

PS another important thing to consider - are the pet stairs carpeted?  If they are not, your dog may feel that he/she is slipping on them.  You might want to carpet the steps.