Sprint Nextel is making a big push to help customers understand their phones, creating a formal program to make store employees available to explain their products and set them up for buyers. The campaign to be announced Tuesday is the first official program for in-person help by a cell carrier, but is similar to moves in the wider consumer electronics industry to demystify gadgets through one-on-one contact. Sprint closed all of its 1,219 stores on Sunday Aug. 17 to train its employees for the “Ready Now” program.