How do you use the vector start it pro to charge a battery

I know how you feel because I had the same problem with mine until I read about the procedure.
Most of those Jump start chargers unfortunately require that you charge them when you buy it and then maintain the charge at least once a month.
There is usually a light on the charger to indicate that the charger is fully charged.

The overall verdict is this is a poor quality jump starter which has an unreliable charger and a battery that will die if you don't look after it. However, I found one fair report on Amazon amongst many bad ones:
"The compressor on this unit, like so many others this small, is really only made for pumping up toys or bicycle tires. So don't buy this unit for that purpose. Go to a gas station with quarters and use their air vender.
If, like me, you bought a used unit, you will need to get both the manual and the charger. Do a search on servicenet dewalt to find the owners manual. The manual is a download pdf. Charger model number is 514005-42.
Hope this helps. It's really a neat little device to have around. I especially like the built-in LED flashlight.
You really NEED to read the manual all the way through. The special sealed type battery requires charging at least every 60 days or it WILL go bad quickly."
The Manual is here: http://documents2.dewalt.com/documents/English/Instruction%20Manual/Vector/VEC010BD.pdf
Because I'm an engineer I know I could easily replace the 12v lead-acid battery charger, open the box and replace the battery with another 12v say 200 Amp cranking (short circuit effectively) battery but I would tend to spend a bit more on a gel battery of similar spec 'cos it basically is the only sort that should be used for deep cycle discharge with such a small volume battery. Good luck.

How old is it? If it's more that 2 years old the battery needs to be replaced.

I HAVE A NEW SUCH PRO UNIT WHEN I WENT TO USE THE CHARGER THAT CAME WITH IT IT WILL NOT WORK CAN I GET ANOTHER CHARGE UNIT SEN T TO ME ??

It's a 12 volt gell cell battery. Radio Shack sells them among others.

The battery inside is easily replaceable Just open it take out the battery and get a new one from Radio Shack .

The battery needs replaced. In March, 2006, Black & Decker purchased Vector Products, Inc. Since the acquisition, Black & Decker has assumed the manufacturing of all Vector products. For customer service and warranty information for Vector products, please contact Black & Decker Customer Service. Or, you can order a replacement battery from: www.batterymart.com/p-6v-4_5ah-sealed-lead-acid-battery.html

http://www.baccusglobal.com/bd/manuals/NEW%20MANUALS%20FOR%20WEB/VEC012POB%20MANUAL.pdf

Most likly the battery is old and will not keep a charge. I just replaced my battery for about $50 a few weeks ago. Go to a story like Battery + for a replacement. It worked for me.

Easy, just insert the "cigarette lighter style" plug from the A/C charger into the "cigarette lighter style" socket on the top of the unit, and then insert the A/C adapter in to a wall socket. It can also be charged in your car with a cord that has double "cigarette lighter style" plugs at ether end, one inserted in the Vector and the other in your cigarette lighter.
Wait, one more - clamp the units cables properly on to your cars battery terminals, then start your car. periodicly checking for full charge.
Hope it helps... Good luck