You must go to the warehouse-there is 1 in each city.Look at your map (alt+m).There should be 3 dwarfs-1 of them might have warehouse freithman as a title above his name.If there is no guy just speak to all 3.
The guy that has:Check freight or something close is your guy.Then a box opens up with your other chars on the server and you can put items.It costs 1000 adena for each STACK of items (1000 animal bones are 1 stack-3 spellbooks of might are 3 stacks).Then you go with your other char to a warehouse (no matter which) and speak with the freightman there.You click on the:Claim Freight (just below the check freight) and get your items.
Oh i almost forgot-the items you transfrer count as items put in warehouse storage.Which means that your freight+storage cannot exeed the limit you see when you put items in the warehouse.