Research the funds available (remember that the name of the fund is not always a reliable guide to what investments are being made). The Market Forces website has a list with an independent analysis.
Contact your choice of fund to open an account. Most funds will organise the transfer of your balance for you but you can do this yourself online at the ATO website.
Inform your employer that you have changed your super fund and give them the details. Use the Superannuation standard choice form from the ATO.
NB. Some Government departments and other employers do not permit employees to choose their own super fund. You may still be able to choose a more ethical option from those available to you.