How do I install a custom ROM on sony experia ray ST18i?

I unlocked the bootloader and rooted the device already like this: [How to unlock and root a Sony Ericsson Xperia Ray ST18i with 4.1.B.1.13](https://android.stackexchange.com/a/55944/22975) But How can I install a custom Rom now on the device? I guess I have to enter the recovery menu for it? I tried this, but it doesen't work: > press the volume down key a few times when your phone boots up. The sony logo brightens at one point, press during that time