I see that Expensify is an expense software so I am assuming that you need a way to import AP Voucher transactions to track the expenses in Sage 500.  I would suggest reviewing the Data Import Manager (DIM) procedure spAPapiAPPendInvoiceIns which creates pending vouchers in Sage 500.  It uses staging tables to process the records to be imported.  If AP Vouchers are not what you need to create, what type are transactions do you need?

You will also need to determine how you will get the information from Expensify to Sage 500.  Will Sage 500 be pulling the data from Expensify or will Expensify be pushing data to Sage 500.    Sage 500 doesn't have any web services that interact with the DIM routines, so you will need to take that into account as well.

I see that Expensify is an expense software so I am assuming that you need a way to import AP Voucher transactions to track the expenses in Sage 500.  I would suggest reviewing the Data Import Manager (DIM) procedure spAPapiAPPendInvoiceIns which creates pending vouchers in Sage 500.  It uses staging tables to process the records to be imported.  If AP Vouchers are not what you need to create, what type are transactions do you need?

You will also need to determine how you will get the information from Expensify to Sage 500.  Will Sage 500 be pulling the data from Expensify or will Expensify be pushing data to Sage 500.    Sage 500 doesn't have any web services that interact with the DIM routines, so you will need to take that into account as well.

We need to push data into Sage 500.Is any documentation available for spAPapiAPPendInvoiceIns stored procedure.

You should be able to look at the code of the stored procedure and figure out the process. It has some comments inline in it as well. 

We have not done this for Expensify but we have done this for Concur and Certify. Here is a blog post that may give you some additional information https://www.rklesolutions.com/?s=Concur. You can watch the recorded webinar as well.