You have to have them in the same army or settlement. Then open the scroll of the character with the ancillary you want to transfer. Drag and drop it onto the portrait of the character you want it to go to.

^^He said it. However, that doesn't work for admirals, does someone know how to do it for them?

i tried once to give a retuine that my faction leader had to my diplomat, but it didn't work. My leader had a translator, which i figured would work much better with my dip., i checked to make sure the dip didn't already have it and he didn't, but it still didn't transfer, both were in the same city as well.

For Admirals, you cannot transfer ancillaries in-game through normal gameplay, since admirals can't occupy the same place . You can assign ancillaries in either .txt setup files (e.g., descr_strat.txt), or from the console.

You can, however, assign certian unexpected ancillaries to admirals, spies, and assassins... like explorer. This increases their range of movement, for example.