putting stuff from custom.el into init.el

Hi,

if I want to put e.g.

 '(custom-enabled-themes '(leuven))

into my init.el

what would it look like in my init.el file?
What would I have to change?

Can I simply copy the content of a custom.el file into my init.el file
and delete the content of my custom.el file?

Or what would I have to do to get the settings into my init.el file?

thanks Gottfried