To get admission in PSUs, you will have to clear Gate exam with decent score. Also, the application process and dates vary PSU to PSU so it is advisable to go through the below link to know all about PSUs through Gate and if you talk about job in abroad then please tell which country you are interested in?

And the Gate registration is over for 2018 have you applied for it?

PSU through Gate 2018

Hope this helps!!!