Intro: The new Admin who needs help

[JMR4HOPE]

My introduction to SF was the tutorials and the 4-day Admin training.  I now have a plan for our processes, but I've come to realize that there are certain sequencings required in order for you customizations to work. I've reached a point that the more I read it seems the less I know what to do next.

I just need to clearly see a logical sequence of steps. I have my processes for donation pipeline flow from leads, to opportunities, to accounts.  I need to clearly see what the SF protocols so I can do it right the first time.  I’m a good learning and would appreciate assistance. 

Here's where I am:   I created an object Donation History (donation details) and Payment History (record of payment to a donation) object.  The Donation History appears as a Relate List on the Account page, and the Payment History data appears when you drill down on a donation.  Now, I want to build a custom field on the Account page that will display the total of all donations to-date for this partner.  I find out that there is a master detail relationship that should have been established earlier in the process to enable roll-up or cross over functions. 

Thanks, JMR4HOPE