Ok, maybe not the easiest way bit it's a way that works for people who dont know their ID by looking at Alissa...?
1. Get mod_potato, hint: there are 6 files saying mod_Potato in this download get them all
2. Use mod_potato, hint: put all 6 files into your mod folder and add mod_potato.dll into your mod.txt
3. start mabinogi
4. inside your mabi, in chat window enter /test
5. first line it says ID: 001000000something something, that is your ID
6. antler duping, use alissa and send a packet
0000A9DE<CHARACTER ID>000000
you dont have to build it or anything, just send this packet, with out <> and just put your id in there,
example 0000A9DE001000000somethingsomething000000