Typically your TL or ETL will teach you or at least another SFS TM. The basic process is...
1. Open Pack N Ship
2. Select print and pack and scan all the numbered locations of one cart while in print.
3. Enter into the packing mode and scan the bottom barcode on the shipping label attached to the paper. (The shipping label will be at the bottom of the paper and should have a bunch of barcodes on it)
4. Seperate the rest of the paper from the shipping label (They are supposed to be torn apart from each other)
5. Follow the apps instructions on what items you are meant to get from that order.
6. Grab the appropriate box size for the order (The packing slip with the order info has a box size reccomendation typically found on the bottom left of the paper)
7.Tape the bottom of the box closed and begin packing the items.
8.Put the packing slip paper into the box before taping the box shut. DO NOT put the shipping label inside the box.
9.Once closed, stick the shipping label to the outside of the box and repeat until you've packed all your orders.
This is a super basic guide and doesn't go over a lot of the other SFS things to know like packing hazardous and fragile materials, using manhattan, making deadlines, etc. Ask your TL or ETL to train you throughly in SFS, it really helps in understanding the process and makes you an invaluable asset to your team throughout multiple points in the year.