Here is how you can enable trim in el capitan
Apple does not recommend this but they never recommend anything like this for third party hardware. I have been running TRIM under el capitan since it came out without issue.
If you do not enable TRIM you will need to make sure the drive has sufficient idle time so it can perform garbage collection. before enabeling trim in MAC i would leave the computer on over night and only sleep the monitor so the drive could run garbage collection.
There are FW update threads stickied at the top of each SSD board. Here is the FW thread with instructions for updating in Mac