In general, when you're trying to figure out how to automate something in Sage 300, you can record a macro of the process. That will generate VBA code for you that you can then generalize and translate into the language that you're using.

For posting batches there are a couple of ways. One is to open the Post Batches view and pass it the batch numbers. In the case below, AR0048 is the Post Invoices view.

    Dim PostBatchView As AccpacCOMAPI.AccpacView
    fDBLink.OpenView "AR0048", PostBatchView

    PostBatchView.Fields("BATCHIDFR").PutWithoutVerification BatchNumber
    PostBatchView.Fields("BATCHIDTO").PutWithoutVerification BatchNumber

    PostBatchView.Process

In this example, I'm trying to lock access to the AR receipt batch before setting the status to Ready to Post. Then I call the Receipt posting view.

    With ReceiptBatch
        .Fields("PROCESSCMD").PutWithoutVerification ("3")    ' Process Command
        .Process
        .Fields("BATCHSTAT").value = "7"                      ' Batch Status
        .Update
        .Fields("PROCESSCMD").PutWithoutVerification ("1")    ' Process Command
        .Process
    End With

    Dim ARReceiptPost As AccpacCOMAPI.AccpacView
    fDBLink.OpenView "AR0049", ARReceiptPost

    ARReceiptPost.Fields("BATCHIDFR").PutWithoutVerification BatchNumber
    ARReceiptPost.Fields("BATCHIDTO").PutWithoutVerification BatchNumber

    ARReceiptPost.Process

See my response to your duplicate question:

https://www.sagecity.com/us/sage300/f/reports-macros-and-customizations/208664/how-to-post-the-ar-or-ap-batch-using-accpac-advantage