How do I integrate a logo (image) in the general configuration for the system dashboard?

[Taylor]

I have posted my image on the ssh into the server /opt/atlassian/jira/

I do not know how to now integrate that into the introduction gadget which has HTML. 

I am also trying to insert the users guide HTML into this gadget and it is not mapping the link. 

Please advise. We are so close to launching our JIRA to our team!