Do I need to configure any settings in BUSY to start generating e-invoices?

Yes, you have to configure e-invoice configuration in BUSY
Please check the below configuration option of e-invoice:
1: Go to Administration and click on configuration.
2: Select Features / Options and click on GST / VAT, here you will see a option called E-invoice Required.
3: you have to selected Y to turn it on and mentioned your place and pincode, all required and user restrictions in configuration window of E-invoice and then clck on GSP configuration Tab then you have to entered GSP username and password (wich you have to create on E-way bill portal) and check through validate both id and then save 
4: Go back to Administration and click on configuration. 
5: Choose the Voucher Series Configuration option and select the voucher type for which you want to generate e invoice, such as sales, sales return, etc. and select series & then click on voucher configuration then check generate E-invoice after saving is enabled or not, if not then you have to enable it.
6: Again Go back to Administration and click on configuration.
7: invoice/document then select standard if you are using standard invoice for printing then click on sale invoice and then check print e-invoice IRN/Ack no. and Ack date and print E-invoice qr code both options enabled..