What you've been given is a Certificate (the public part, signed by a trusted party) and the associated key (the private part). In simple terms it's the private key that allows your app to sign stuff in a way that the remote party can then validate using the public part, the certificate. Your server needs to have both linked together so that protocols like SSL\TLS can work properly.
In your case you have been given a complete pair, not just the Cert. The format you have been given it is called PEM and unfortunately Windows Certificate Manager can't import that natively (to the best of my knowledge).
The quickest way I've found to convert it is to install OpenSSL somewhere and convert the file you have to PKCS#12 format using the following command. You will need to break the file you got from the CA into two parts, one containing the certificate block called "certificate.txt" and and one containing the private key block called "key.txt":
openssl pkcs12 -export -out mycertkey.p12 -in certificate.txt -inkey key.txt
Once you have the PKCS#12 format file you can import it into Windows:
- Open the MMC ( Start -> Run ->
MMC.exe ) and then select add\remove
snap-in and add in the Certificates
- Select "Computer Account" as the
- Right click the "Personal" folder and
select the "Tasks>Import"
- Find the mycertkey.p12 file you
created and import the certificate
and private key into the Computer's
Once the cert is installed you can now assign it from within IIS (this may vary a bit depending on IIS version)
- Open you IIS Management Console and
right click the domain you want to assign
the certificate to.
- Select Properties
- Select the "Directory Security" tab, and
then "Server Certificates"
- Follow the Certificates Wizard
prompts, selecting Next, then
select "Assign Certificate" and then Next again.
- Find and select the certificate you
have just imported and click OK.
That should do it.