AlegroCart

I can't seem to figure out how to actually add a coupon, and a search for "coupon" in this forum didn't return anything that helped me with that. Also, can a coupon be applied for just selected items, and not as an across the board discount for the entire catalog? Maybe that will be obvious once I learn how to add one. TIA for any help.

Go to Admin->Customers->Coupon.
Click Insert.
On the General Tab add name and description.
On the Data tab enter Code that is a number (e.g. 6665 or whatever you want). You have to share this number with your customer(s) to apply the coupon.
Discount could be set in % or in constant value.
Under Minimum Order Value (in your default currency) the coupon cannot be applied (if you set. Leave empty to not use).
In the Valid Products box you can select as many items as you want. The coupon will be valid only for the selected items.
To select more items press and hold CTRL while clicking.
Change Status to enabled.
Save your work.