Once you pass your atpl theory,get your CPL/IR and mcc you get a frozen atpl.
To get it unfrozen (basically to get a full atpl licence) you need, if my air law memory serves me right
1500 total time of which
100 hours night
75 hours are on instruments,
500 hours mulit crew
750 hours pilot in command of aeroplanes
One or two more requirments i think
Dont quote me on the above, my air law is a bit rusty.
But in a nutshell, once you have a frozen atpl, you can apply for work as a FO with an airline. You wont be able to get your full atpl until you get a job with an airline or some other operator of multi crew aircraft because of the requirement for multi crew time.