how do i change battery on optima xm alarm?

Eliz, you need a Yuasa 2.1 amp hour sealed lead acid rechargeable battery, available from Screwfix which is probably the cheapest for you, about £12,
As GTS mentions above, make sure you put red connector to red on the battery, Black onto back, close the lid and press reset
If you get any issues just call 07842 480037
This is not my main phone just a spare and it sits in my vechicle but i will call you back.

Nick
June 2011

you may have to key in your pin number to reset,dont know coz we dont use these panels

gts
June 2011

open panel,one screw,remove old battery,fit new one close panel,press reset

gts
June 2011