I'm confused on when and how to apply batches in the system. Can you explain the right way?

In BUSY, you can use batch details feature by following steps:
1.Enable the batch details
Step 1: Go to Administration section then Click on Configuration
Step 2: Select Feature and option then choose Inventory tab
Step 3: Enbale the batch wise details and save the configuration after made required changes.
2.Enable batch option in item master.
Step 1: Go to administration then click on master menu
Step 2: Choose the item option then select modify tab
Step 3: Specify Y to enable the batch details feature and save the master.
3.Post entry with batch details.
Step 1: Go to transaction section then click on purchase voucher type
Step 2: Select the add option then specify the header part of invoice.
Step 3: At body part, after entry the item details and its quantity, batch details window will appear where you need to specify the batch number manually with required quantity.
Step 4: Save the invoice after create with required details.
4.To adjust the batch in sales invoice.
Step 1: Go to transaction section then click on sales voucher type
Step 2: Select the add option then specify the header part of invoice.
Step 3: At body part, after entry the item details and its quantity, batch details window will appear where you can adjust the batch details from drop down.
Step 4: Save the invoice after create with required details.