I have the fisher paykel pepper electric stove top and oven at home. the stove is working just fine, but below it the oven turns on but it doesnt heat up. what should i do?

When you say that the oven turns on I assume that the oven indicator light is working. If this is so there will be only two likely causes for the oven not working.
Oven element is faulty - check by performing continuity test;
Wiring at oven element terminals burnt off - check visually.
If you are handy carry out the above. If not, call a repairman.