To install dropbox follow this link
Once you have dropbox installed open it.
Then right click on part of the blank area in the window and select New - Folder.
Name this folder Bookkeeping.
You will put any of your bookkeeping documents in this folder and you can save your computerised bookkeeping file there too.
Next, right click on the bookkeeping folder and choose Dropbox - Share this folder.
This will open up a webpage where you select who you would like to share this file with.
In this case enter the email address firstname.lastname@example.org then click "Share Folder"
Now I can access anything you put in that folder without having to bother you.
An extra advantage is that If your computer were to crash any files you have put in Dropbox will be saved and you can access them from any computer or smart phone.