My employer's attorney submitted my Labor (PERM) to DOL today. Any idea what will be the next step and how long will it take for me to get the green card under EB-3 category Computer Engineer position.

Check PERM processing time here ..
https://icert.doleta.gov/

Looks like the current time is 5-6 months. If it goes to audit add another 6-12 months.

After that comes 1-40 stage (2nd step). If PP, it will take 15 days else few months provided there are no RFE.

Check below for 3rd step which is i-485
https://travel.state.gov/content/visas/en/law-and-policy/bulletin.html

looks like EB3 for Nepal is almost current..

P.S. Please do some research as well so that it makes more sense the things we talk about.

Stupida is right. PERM approval might takes anywhere between 5-6 months if RFE is not issued.
Once PERM is approved, then you can file for I-140, I-131, I-765 (EAD through GC), I-140 can be filed concurrently with  I-131, I-765 (EAD through GC),I-485 to save time if you are sure that I-140 will be approved, otherwise I recommend not to file for concurrent filing because if I-140 is denied, all your other applications (I-131,I-765,I-485) will be void and you lose lots of money during that process.