Let's go over this step by step. Suppose say you want to lock some bitcoins in a 2-of-3 multi-sig.
Create a multi-sig script: OP_2 <pub_key 1> <pub_key2> <pub_key3> OP_3 OP_CHECKMULTISIG.
Hash the multi-sig script with HASH160 which gives you multi-sig_scripthash.
Base58Check the multi-sig_scripthash with version 0x05 ...