We have an Outfit system which means you can create new Outfits to switch to and from. To make a new Outfit, click on the Outfit button. Once the Outfit window has opened, go to the left hand side and you will see there is a 'New Outfit' button. Click on this button.
There will be two boxes, one that says 'Enter a Name' and another one saying 'Base Male'. Enter the name of the outfit, such as 'Outfit One', and then using the dropdown button next to 'Base Male', you can choose the outfit to be for 'Base Male' or 'Base Female'.
Once you have done that, click on 'Create'. You can then change the hair, clothing and accessories on your avatar for this outfit, then 'Save and Close' to have this outfit always saved for whenever you want to use it.
You can also use the dropdown menu at the top to see all the outfits you have made, and use the 'Switch' button to switch to another outfit.