To define your security settings and to specify which certificate you wish to use you need to define your default security settings. To do so you need to click the ‘Change Settings’ button. You will then receive the following screen :

You can create different security settings and give these separate names to be used for different purposes. 

The ‘Digital Signature’ section of this window allows you to choose the certificate that will be used to sign your emails. You need to click the ‘Choose…’ button to receive the following screen: 

This screen allows you to define which certificate is to be used in the digital signing process in the settings you are defining.
You can view the certificate by clicking on the ‘View Certificate…’ button. You will then receive a screen that gives an overview of the certificate. This will be similar to the following picture: 

The ‘Digital Signature’ settings section also allows you to define which type of hashing algorithm you want to use for the creation of your signatures (SHA-1, MD5) 
The ‘Encryption’ settings allow you to choose a certificate which will be used to sign your emails. You need to click the ‘Choose…’ button to receive the same screen as presented previously. 

Digitally signing Individual messages with Outlook  
To sign your e-mail messages individually, click the ‘Options…’ button in the e-mail window: 

Click the ‘Options…’ button to get the following screen : 

This screen allows you to set specific options for the message you are composing. These options include whether the email should be encrypted and whether a digital signature should be added to the outgoing message. 

Encrypting e-mail messages with Outlook
You can encrypt your messages individually each time you want to send an encrypted message, or you can configure security options so that your messages will be automatically encrypted every time the recipient’s digital certificate is available in your address book.  This is done by following the instruction similar to Digital Signatures but with selecting the encryption options 

Saving digital certificates from  signed message.

When you receive a signed message, you can save the digital certificate of that person in your address book. You first need to click on the signed icon 

This will give you the following screen : 

This screen gives you more information about the certificate that was used for signing the email in se. If you want to view the certificate and all its detail, you need to click the ‘View Certificate…’ button. This will give you a screen which is similar to the following:

Clickon the ‘Details’ tab to go the following screen: 

At this point if your click the ‘Copy to File…’ will store the certificate to a file that you can import by following the next instruction set. 

Save a digital certificate from an encrypted message.

When you receive a signed encrypted message, you can save the digital certificate of that person in your address book. You first need to click on the signed icon

This will give you the following screen :

Click on the ‘Encryption Certificate…’ to open the  ‘View Certificate’ window described in the previous section.  Follow the same instructions to save the certificate to a file to be imported in the address book. 

Importing a downloaded digital certificate.
To import digital certificates: 

1. Create in Outlook  a new address or open an existing one in your address book 

2. Choose ‘digital IDs’ 

3. Choose ‘import’ 

4. Select the downloaded file with the digital certificate and choose ‘open’ 

To remove a digital certificate from your address book:

1. Open the address of the person whose digital certificate you want to remove. 

2. Choose ‘digital IDs’ 

3. Select the certificate you want to Delete 

4. Click on ‘remove’