unzip this into %appdata%/.minecraft/versions, so you have a folder named "a1.1.3" with the json and the "put_in_jar" folder inside it.

Using the minecraft launcher, download a VANILLA alpha 1.1.2_01, load the client, then close it and the launcher completely.

Copy the "a1.1.2_01.jar" from the a1.1.2_01 directory in .minecraft/versions and paste it into /a1.1.3

rename the jar to "a1.1.3.jar", without quotation marks.

Open the jar with your archive program of choice (winzip, 7zip, winrar), delete META_INF, and drop the contents of "put_in_jar" into the jar.

If you've done everything correctly, then close everything, open the launcher, find "old_alpha a1.1.3" in the version list, and play!