Write to a file that i am reading from

So the problem is, that, i am reading from a file and am placing it into arrays. How am i suppose to edit the file using a gui that i will be creating?

For example:
There is this cd file that i am reading from, and have placed the title, singer, price, discount and all on the array and this details will be displayed in a gui. I need to create a gui, to edit the cd title and save it, then add tracks to the cd and etc. I would like some suggestions on it.

Thank you, for your help, really appreciate it

Read file to memory
Edit data
When done write back to file