Converting to Fixed Asset Manager

I have a company that has been on QB for years, but depreciation was handled through other software. How do I enter the accumulated depreciation in the Fixed Asset Manager so that it is historically correct and calculating correctly going forward? (The historical detail is in the G/L, i.e., accounts and subaccounts for A/D, etc.) My concern is how to setup so that FA Manager correctly calculates the remaining depreciation for items only having one or two years of depreciation left.