Hi, I have some questions regarding posting my year end adjusting entries.  

I started using Sage May 1, 2019 and set up our company from fresh. I am not a bookkeeper and am still learning the Sage program.  At May 1st, I entered the opening balances from the previous years trial balance which had been done by a previous bookkeeper.  I have been doing all entries to date using those opening balances.  Long story short, we have just had the year end financials prepared by our accountant and there are some year end adjustments that need to be done for the year ending April 30, 2019.  He also found that there was HST that was never claimed when a company vehicle was purchased in 2018 and has advised it can be claimed on our next return. It is in the approximate amount of $4800. 

Questions

#1   How do I post the HST that was missed in Sage 50 so that it shows up on my next HST report?  

#2    How do I post the adjusting entries, step by step?  I attempted to do it but some of the accounts are "control accounts", e.g. accounts payable so they are not showing up when I try to enter them as a journal entry.

#3   I was also given a list of opening balances by the accountant to enter in on May 1, 2019.  Can I go back and change my opening balances now for this current year and if so, how do I enter these correctly.  I am confused if they should be entered as debits or credits.    

Any help would be appreciated.