Hello,
Have you tried the following steps:
Step 1 
Use the openssl toolkit to generate an RSA Private Key and CSR (Certificate Signing Request). The RSA Private Key is a 1024 bit key which is stored in a PEM format. The following example shows how to generate the RSA key.
openssl genrsa -out server.key 1024
Generating RSA private key, 1024 bit long modulus
.....++++++
.................................++++++
e is 65537 (0x10001)
Step 2 After generating the RSA key, generate the CSR. The following example shows how to generate the CSR.
openssl req -new -key server.key -out server.csr
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [GB]:US
State or Province Name (full name) [Berkshire]:California
Locality Name (eg, city) [Newbury]:SanJose
Organization Name (eg, company) [My Company Ltd]:Cisco Systems
Organizational Unit Name (eg, section) []:Org
Common Name (eg, your name or your server's hostname) []:
Email Address []:
Note Make sure the generated certificate is not shared and it should be protected.
Step 3 The CSR file can be used to generate a signed server certificate from a certificate authority (CA) or you can generate a self-signed certificate.
Step 4 To generate a self-signed certificate, use the following command.
openssl x509 -req -days 365 -in server.csr -signkey server.key -out server.crt
Signature ok
subject=/C=US/ST=California/L=SanJose/O=Cisco Systems/OU=Org/CN=
Getting Private key
For more information, please have a look at the following cisco doc:
