The problem is I don't know they mean by that.
That is probably because you don't know how AES works which means you probably shouldn't implement BIP38 yourself and try to use an existing library that is well tested even in another language.What the quote means is that you use AES with the following settings:
key size = 256 (bit) (the derived key from scrypt)
mode = ECB (each block is encrypted individually)
IV = new byte[16] (empty initialization vector)
padding = none
When decrypting, you split the decrypted key (extracted from the base58) into 2x 16-byte parts and decrypt using the AES instance you prepared above in 2 rounds to get the 2x 16-byte chunk of the actual private key.
