Overall this looks like a great start. However, consider the following points to help streamline the UX making your design more efficient and easier to use.
If possible make one purpose per page. You don't want a password form validation error scenario on the Promo Code page. One purpose pages are also favorable for keyboard/enter form submissions. Minimizing mouse-keyboard switching is efficient.
Why not just put 'Change Password' under the 'My Account' page?
If you are going to allow the user to change their password, for security purposes, confirm that they are the account owner. Forgot Password and Change Password are two different cases with slightly different requirements.
GitHub is a good example:
Consider each element on the screen carefully.
As a general rule, anything that can be removed, should be removed. It serves to distract the user, which can lead to confusion and frustration.
Your sketch appears to be a page that the user has already entered their credentials. 'Change password' does not have relevant context here. And reconsider the out-bound links ("Theme by...") as a siphon taking the user away from the task at hand.
If there are really only three things going on, that's all that should be there. Think about the user's experience. Do they really care whose theme it is, or is it more important that they use their promo codes?