Is this the correct process to start selling on Amazon?

I’ve done my research but before I pay for anything Amazon related I want to make sure I’m on the right track.

I have sourced a product and received trial units (not my own brand). The packaging has barcodes on already but when I have tried to enter this on Amazon it comes up with a different product.

I need to buy a GS1 annual memebership for £120 which is 1000 product barcodes I believe.

Do I print these out?

I add the items to my inventory using the gs1 barcode.

I arrange a courier to collect my items and ship to amazon.

Let the sales come in…

Is this right?