hi...
how to change username, password ,address,city in vb.net form

If you are storing this data into a database (SQL, MySQL, Access)

Execute an update statement:

"UPDATE table SET username='" & txtUserName.Text & "', password='" & txtPassWord.Text & "',address='" & txtAddress.Text & "',city='" & txtCity.Text & "'"

Or you can parameterize the query.

"UPDATE table SET username=@username, password=@password,address=@address,city=@city"

'To enter data, just use the AddParameter function

cmd.Parameters.Add("@username",txtUserName.Text)
'ect...