This is the quick and dirty method, can usually be done without removal from the action, these springs are held in place by the flange screw.  Simply back the screw out several turns, insert short, hooked part of spring around the screw (under the head) and then tighten screw.  Make sure slightly curved end of spring is in the slot on the damper lever.  May be strengthened or weakened by slightly curving or straightening. Fits uprights with full size damper levers.

If you're looking for the factory style springs check my eBay store - I offer medium and heavy strength springs in quantities of a dozen or a set of 70 (there are 88 notes on a piano but only about 65-68 usually have dampers).

I've been a tech for 30+ years and am glad to help before or after the sale.  I include my contact info in each shipment and you can also reach me through eBay.