You can encourage the bees to use the frame of older pollen by placing it next to or between two frames of open brood. The pollen should receive preferential use for two reasons: 1, proximity to larvae that need it for feed, 2. a desire to make room for the queen to lay new eggs in the active brood area.
However, when doing this, I wouldn't put more than one frame of old pollen in each split. Too many frames of pollen can also have the effect of serving as a wall to prevent expansion of the brood nest.