There are two considerations: a) to make certain the electrical work goes OK and, b) to make certain the thing is safely attached to the ceiling. a) during good dailight switch your light on then go and remove the main lights fuse (or trip circuit breaker) governing this light - it will go out when you have cut the power, meaning you should be safe to wade in (assuming wiring is not dangerous). Uncover el connections, note arrangement (colours of wires, connection technique, etc. for education purposes) and disconnect the wires making certain you don't lose the feed wire to the light (tie it so it protrudes, if necessary). Free the old fixture from the ceiling. b) ensure you can securely fit the new fixture and do as much as you can to fit it making sure access remains for the wire connections (sometimes both operations need to be done somewhat simultaneously). Now back to a) you need to connect earth to the earth terminal which is identified by a type of arrow symbol made up of lines of differing length. Then you connect the incoming live wire to light fixture live wire and similarly the two neutral wires also. Earth wires are either yellow and green or pure green, and on normal power supply cables (from the ceiling) have a naked copper conductor (which should have a piece of green plastic sleeving around it). Live wires are normally red or brown and neutral either black or blue. Make certain none of the three wire types interconnect and that the joints are well insulated - best use a small connecting block capable of taking the wire sizes involved and one which will fit into the cover by the ceiling. Note that some light fittings do not require an earth connection, but most do. If you have problems post them here, I will try to keep a watch in case I can help further.