When you create a certificate, you can specify whether it is exportable. If a key is exportable, it can be extracted and put in a file along with the associated certificate. The file is written in an industry standard format, PKCS#12, which allows it to be transported to other platforms. It is encrypted with a user-specified password to protect the private key. You can export private certificates to obtain a backup copy of the key, to move the key to a different server, or to share the key between servers.
You cannot export a certificate if you enabled the Do not allow private key to be exportable option while creating the certificate.
Click Security > Certificates.
On the Certificates page, click the certificate.
On the Certificate Details page, click Export Private/Public Keypair.
Select a format for the key:
PFX/PKCS12: Public Key Cryptography Standards #12 (PKCS#12) format, which is also called PFX format. This format can be used to create JKS or PEM files.
JKS: Java keystore format.
Specify the password in the Encryption/decryption password field, then click OK.
IMPORTANT:Remember this password because you need it to re-import the key.
Click OK.