there, Am trying to accomplish something but am stuck,

Hi there,

Am trying to accomplish something but am stuck, maybe you might know how to help me. Im trying to allow users to update their profile in a page , already create the html form and display to the logged in user his/her email, displayname, username etc.. But i dont know how to allow the form to be submited, i want the user to be able to update the following information:
1.email
2.password
3. Lastname
4. First bame
5. Maybe biography

And also if a user is changing his/her password , for security reason i want it to make sure that the user enter their current password and check if its correct before updating the new password..

I know thats alot but if you can point me to the right direction i will be fine.

Cheers,

Thomas