Answer
The first step is the protonation of diethyl ether. A lone pair on the oxygen of the ether will attack the H of HBr. The initial products are Br- and CH3CH2-OH-CH2CH3 with + charge on oxygen.
Work Step by Step
The Br- then attacks one of the CH2's to form CH3CH2Br and CH3CH2OH becomes the leaving group.