Step 1: First note that this works well with big world. Ok take half of your nukes and put them somewhere off to the side AWAY from your citys. Take the other and put them in a different spot also far away from the citys. This means puting silos on the islands leading to Greenland if you're N.America.
Step 2: By this time you should still be in Defcon 5. Like silos also put your airbases away from the major citys.
Step 3:Fleets, most likely the most important part of Defcon. Get groups of ALL subs. Have these move away from your enemy. Same rule. with carriers have these move as far away from the enemy as possible. Then you should only have battleships left. Use these to attack the incoming enemy navy while your subs and carriers get away. Keep this in a place far far away from the battle like if your fighting Russia with N.America hide your ships in the mid Atlantic or Indian Ocean.
Step 4: Wait until Defcon 3. Use your battleships which should still be at your coast to fight off the enemy's navy.
Step 5: Wait again until Defcon 1. Once you see the enemy launching nukes wait until you an see them streaming down your radar. Then using your silos
aim for the enemy's silos that are launching at you. DO NOT I REPEAT DO NOT USE YOUR SUBS OR CARRIERS OR AIRBASES YET!!!
Step 6: After the dust settles check and see what you have left. Get your carriers to launch fighters around them to scout. If its safe move as close as possible to the enemy's coast. With the subs move with the carriers. AVOID CONTACT WITH ENEMY SHIPS! YOU WILL NOT WIN!! Ok once you are within striking range of your enemy's major citys launch your bombers at the one with the biggest population that you can hit. While your bombers are rearming use the subs to strike the other citys while always going for the city with the biggest population. (example I hit Moscow and now Leningrad has a higher population than Moscow. I would then strike Leningrad until another city has a bigger population.) Keep on doing this until you run out of nukes.
Step 7: By now the victory timer should have started. If you are ahead with nukes left sure go crazy and launch everything. If your are behind with nukes also go crazy except go for the biggest remaining citys. If you dont have nukes then wait until the timer runs out.
Step 8: Cross your fingers because it going to be close. Please reply its my firt post.
, you can face. 
You definitely need naval battle training. 
