First of all, you should try your best to know the basic reason that has caused trouble. However, before making inspection you need to turn the power off. It is better to remove the power plug of the oven from the socket.
If you observe that the element in the oven is out of order or has expired then you need to replace it with the new element. You should hold the bracket firmly and take out the screws that are usually placed on the back side or top of the oven.
Gently pull the element from the oven and stop pulling when you see wires that are behind the element. Carefully unscrew the leads or wires and take out the expired or out of order element.
Take this expired element to the market which will help you to bring the similar new element. It will also help you to avoid mismatching the size of the element.
Now you should attach the wires to this new element making sure that you do not stretch the wires more than the requirement.
You should line up the element in the proper sequence before putting the wires back into their place. Always recheck to avoid pinching wires between back wall and the bracket of the oven.
Now you need to fasten the brackets on the oven and make sure that you have made them properly tight because loosened brackets can cause trouble and the oven will not work properly.
After replacing the element and fixing the brackets properly, you should restore the power by plugging in the switch to the socket. Your oven is ready to use now.