I can't war in civ iii read the war academy but how many units/what type/in what order do i use.
Short Answer: Read the Manual and then read the War Academy.
Simple Answer: Use lots of units with high Attack. Eventually - assuming your Attackers are better than the AI's Defenders - you'll win.
Better Answer: Post a Save showing a typical (for you) attack force. Someone here will tell you whether it's a good ratio of units, whether you should be better prepared, whether you should even be attacking at that point, etc.
Long Answer:
How many units you need depends on who you're fighting, what your comparative Ages are (which dictates unit choice), the size of your empire vis-a-vis your opponent's, terrain, strategy, and tactics. For example, if I'm a Modern Age superpower with Nukes and Modern Armor, I only need to send a few MA against a newborn English AI with only Warriors to defend with. If I'm the Celts facing Persia in a duel to the death in the Ancient Age, I'll want a decent superiority of troop strength - Gallic Swordsmen will probably lose to Immortals if the latter attack, so I'll want the numbers to storm each individual city before reinforcements can get there. If I'm the Russians at the turn of the Industrial Age trying to grab some Coal from a mid-Medieval Iroquois AI, I'll be fairly safe with relative evenness of army size, as Cossacks should be able to deal with the small force I expect to face when taking a single town from the enemy.
The latter examples assume relative equality in Empire size, and all examples ignore the possibility of allies being brought into the war on either side. If you bring allies into the war, you will typically need fewer troops (although your allies probably won't be helping too much, or will help too much), while additional enemies require you to have an advantage of some kind, either in technology, numbers, or terrain.
For example, if you have a small hill/mountain chokepoint connecting you to your enemies, it's a relatively simply matter to fortify only two-three units there with either Forts or Barricades - with the 50% bonus from a Hill, another 50% bonus from the Fort, and a 25% bonus from Fortifying, a Musketman (Defense 4) will be defending with an effective 9 Defense, making him more-or-less safe from everything before Tanks. They are forced to try to sledgehammer their way through your defensive line, and they'll lose a lot of units trying it.
Strategy has to deal with both the units you employ and the way you attack. For example, whether or not you employ Fast units or Artillery is strategy, along with deciding if you want to annihilate your enemy or simply take a few towns. Tactics is the fine manipulation of your strategy - do you use Artillery to bombard a Town down to redlined defenders, no improvements, and 1 size? Do you attack across the river with your 1-move Attacker, or do you cross and attack with a 2-move unit?
If you're not sure if you can win a given war, the best way to continue it (if you decide to continue it - if you can't win it, it might be better to ask for peace) would be to operate defensively, but get all the other AI to dogpile your enemy.
And I'm bored now, so I'll stop.