Exactly like the Champ explained, in other words, you don't have to do anything, you will get two W2s at the end of the year anyways, which will obviously be reported in your taxes since technically, you are still on payroll of both jobs, whether on leave or not. As far as by reporting, if you meant informing the other employer (if I am not mistaken), well by law you don't have to, just fill out the W4, which you must have done by now, I am sure.
