Where to begin?

Recently I was working with a company that was using spark for within the company. I was an end user so I dont know much about OpenFire and how it works. The person responsible for my server has installed OpenFire in the server and has opened the port for communication. What do I do next?

Next step would be to create a user base. Whether you will create users or groups manually or let them register and manage their contacts by themselves. There is also an option to integrate Openfire with LDAP user base.

After creating users:

Launch Spark, or any other XMPP-enabled IM client, add an account to your client. For the domain enter the name of the server you just installed/ran, which if done locally is probably the name of the machine, alternatively you may have established a DNS to use. That should be enough to get you logged in.