Hi Nihad
This is where working with your GP partner is the best route as they have the experience to guide you on this course with best practices so no mistakes are made.
My approach would be to upload your opening AR & AP transactions or if you don't have the functionality to upload, manually (ouch) enter the opening balances.
In order to upload and post you need to have a balanced entry. For opening balances it isn't worth the effort to figure out which is the correct GL distribution especially for payables as these transactions have already been processed and posted to the GL.
I like to use a clearing account or a special setup account so if the transaction is ever voided it stands out like a sore thumb as the clearing account or setup account should never have a balance in it.
You opening transactions should go into a batch so that you can validate the entries before posting.
Once you have validated your batch and it is correct, go to the Posting setup and turn off the posting to GL for your receivables and payables. You do not want these transactions to hit the GL.
Post the batch. Validate the posting and then make sure you turn the posting to the GL back on.
As you are on GP 2016 use the GL Excel copy and paste to create a journal entry that has your closing February Trial Balance. Post this.
Now your AP and AR subledger should tie into the GL control account for each.
If you are using multicurrency then there are other considerations as well since you will be dealing with source currency and translation to functional currency.
Bank Rec is similar. It is a subledger. You will need to have your end of February outstanding Cheque list and deposits in transit and have then entered into Bank Rec.
You will need to enter a plug entry into bank rec to balance it to the GL balance.
Again, you will need to turn off the posting to the GL so that the bank rec entry does not hit the GL. If you have chequebooks in other currencies you have to consider the source amount and the functional amount.
Before doing any of this, I would suggest you have a good backup of your database. Once you have completed each step and are satisfied, make another backup.