You have received a chain of certificates (digital IDs – including your new digital ID).
On pressing "Install" button from your Outlook or Internet Explorer the received applet will install the certificates (digital IDs) into your system and will associate your new digital ID with a secret key that was generated when sending a certificate request.
After that, your digital ID and private key are ready to be used with any application that works with Windows' cryptography. You should just configure your software to use the digital ID.
To configure Microsoft Outlook Express you should run Outlook Express, go to the "Tools"->"Accounts"-menu, click the "Mail" – tab, select your account and click "Properties". In appearing window, go to the "Security" – tab and select a digital ID for digital signing and encrypting your email.
To configure Microsoft Outlook, you should run Outlook, go to the "Tools"->" Options" – menu, click "Security" – tab, click "Settings" – button in "Encrypted e-mail" part. In appearing window, select a Signing Certificate for email digital signing and Encryption Certificate for email encrypting.
Besides, you are able to export your certificate and private key into PFX or P12-files – to create a backup copy. Run Internet Explorer, go to the "Tools"->"Internet options" menu, click the "Content" – tab and click the "Certificates" – button. In the opened window you will see your certificate and you will be able to export it.c of certificates (digital IDs – including your new digital ID).