On the mobile device you may create a purchase order. That is at Dashboard > Buy
Dashboard > Buy
Type quantity > Finish
Save
If you touch the amount you may change the quanitity or the cost of the item
Edit quantity or cost > Finish
Touch the icon to receive the items into the inventory
On the web version you may create the purchase order for your supplier. That is at Main menu > Purchase orders > +
Main menu > Purchase Orders
Purchase > Plus sign
Type the quantity and then Save & Continue (You may select a category o the Supplier)
Click on Finish
Now on web you may add the shiiping date, cost andf notes on the purchse order
Select the purchase order just made
Click on the receive icon to enter the quantity into the inventory
Remarks: when your license is Multi-Wearhouse select the whearhouse where you are going to receive the items from your supplier.