Generate the RSA key

Run the following commands to create a directory in which to store your RSA key, substituting a directory name of your choice:

mkdir ~/domain.com.ssl/
cd ~/domain.com.ssl/

Run the following command to generate a private key:

openssl genrsa -out ~/domain.com.ssl/domain.com.key 2048

Create a CSR

Type the following command to create a CSR with the RSA private key (output is in PEM format):

openssl req -new -sha256 -key ~/domain.com.ssl/domain.com.key -out ~/domain.com.ssl/domain.com.csr

When prompted, enter the necessary information for creating a CSR by using the conventions shown in the following table.

Note: The following characters cannot be used in the Organization Name or theOrganizational Unit: < > ~ ! @ # $ % ^ * / \ ( ) ?.,&

DN field	Explanation	Example
Common Name	The fully qualified domain name for your web server. This must be an exact match.	If you intend to secure the URL https://www.yourdomain.com, then your CSR’s common name must be www.yourdomain.com. If you plan to get a wildcard certificate, make sure to prefix your domain name with an asterisk, for example: *.domain.com.
Organization Name	The exact legal name of your organization. Do not abbreviate your organization name.	domain.com
Organizational Unit	Section of the organization.	IT
City or Locality	The city where your organization is legally located.	Wellesley Hills
State or Province	The state or province where your organization is legally located. Do not use an abbreviation.	Massachusetts
Country	The two-letter ISO abbreviation for your country.	US

Warning: Leave the challenge password blank (press Enter).

Verify your CSR

Run the following command to verify your CSR:

openssl req -noout -text -in ~/domain.com.ssl/domain.com.csr

Submit your CSR

Submit the CSR that you created to a certificate authority.

Trouble Shooting:
A really cool list of commands you can run here