Setting an item up to scan
Open the item and put the barcode into the barcode field, either by typing the printed number or by scanning it straight into the box with your scanner. That is the entire setup for anything that arrives with a code on it. From then on the item is found by scan anywhere the item search appears — billing, purchase entry and stock correction all accept a scan in the same way.
Loose stock with no code
Nuts, bolts, fittings, wire cut to length and most locally made goods arrive with nothing printed on them. Generate a barcode against the item, print a label, and stick it on the bin or the shelf edge rather than on every piece. Scanning the shelf label at the counter is as quick as scanning a product, and it also solves the case of the same item from two suppliers at two rates — each becomes its own item with its own code, so stock and margin stay honest.
Scanner, or the phone camera
A USB or Bluetooth scanner behaves as a keyboard, so it works in the billing screen with no configuration at all — plug it in and scan. On the Android app the phone camera does the same job, which is what most small shops start with before deciding whether a scanner is worth it. Both routes end in the same place: a completed bill line with nothing typed.
What it does to your stock figure
Every scanned line reduces stock when the bill is saved, so the closing figure is produced by billing rather than by a separate counting exercise. That is the only arrangement under which stock in a many-SKU shop stays accurate, because nobody is going to count eight thousand items by hand. Minimum levels on your fast lines then give you a warning before something runs out.