VisualBasic 2010Express Password Read Character and append from textfile

I'm not sure of the code because I've done very little next to nothing within VB2010 with file handling, what I'm wanting to do is make variables to hold them for passwords for the login system because I've tried using a database however there's updating isuses using the database.

I'm wanting to make a variable be the same as the first line of the text file then I want that variable to be the password for the admin or student and I also would like to be able to append the files so that I can edit them from another form.

I can give more information if need any help is appreciated

Thank you