NOTE: If you were logged into the Scratchbox machine before you were added as a Scratchbox user, you need to re-login to your machine, so that you get 'sbox' group privileges needed for running Scratchbox. You can check this by running the following command:
$ groups
If it prints out sbox group name, you're ready to run the Scratchbox.
All you have to do is:
$ /scratchbox/users/username/run.sh
When you run this for the first time it will copy the terminfo terminal capability database to your home directory inside Scratchbox and do some checks and initializations before starting the Scratchbox sandbox.
Because Scratchbox is fully self-contained sandbox, it doesn't inherit anything from the outside system except the environment variables. So, now you can copy your configuration files from your normal home directory into your home directory inside the Scratchbox (/scratchbox/users/$USER$HOME/): ~/.bashrc, ~/.bash_profile, ~/.inputrc, ~/.cvspass etc. Just make sure that your configuration files do not override settings defined in /scratchbox/etc/profile file inside the Scratchbox.