l admit I am useless when it comes to cars!I've got the new battery and l assume its a case of clipping it in and putting on the positive and negative wires but I am worried about electricuting myself so please help!

A car battery is only 12 volts & this is such a low voltage that it will not be able to harm you.
There r a few points more to simply disconnecting the old battery & replacing it with the new one though.
Make sure u know ur car radios security pin number as if u disconnect the battery u may find the radio will not work until the pin is re entered.There is a way around this if u get some jump leads u can swap batteries around without disconnecting power from the terminals & thereby not needing to re enter the pin number.
Simply be care full & u will be fine.

you cant get a shock,just make sure your ignition is off when your connecting and disconnecting and you will be fine,it can only go on one way usually,its straight forward enough,you will see,good luck..

Make sure that the old and the new batteries have the positive and negative terminals in the same positions,sometimes they are on different sides.