OK, i turned my Steel Sword into a fire sword. After using it (hardly ever) i got a message saying it needs recharged. My questions:

Whats that about?
How often do i need to recharge it?
How do i recharge it?
Is it worth the hassle?

Bump, i need the help

Enchants that fire when you use them (such as fire damage whenever you hit something) use up the charge on the item. Your sword has a limited charge. Once you have expended that charge, it won't do any fire damage until you recharge it. Soul stones (that actually have souls stored in them) are used to recharge items. If you go to your inventory and highlight the item in question (your firesword), you'll see a bar beneath its stats (but above the description of the enchantment) that shows you how much charge is remaining. The better the charge on the soul stone you use, the more it recharges your item. I also think there are spells that improve the efficiency of charging with soul stones. Soul stones are pretty easy to find, and it you have an item with a binding enchantment or are a conjurer, filling them with souls is pretty trivial.

Not sure if there are any other ways to recharge items.

You can charge enchanted weapons with Soul Gems. Depending on the size of the gem and the size of the soul it carries, it'll fill a part of the grey bar which indicated the amount of charges the weapon has. You can charge it by clicking on the weapon in your inventory and then, using the shortcut key indicated at the bottom of your screen. Mine is "T". Then you can pick various Soul Gems to charge the weapon. How often you have to charge is depending on how strong the enchantment is (this is determined by the type of Soul Gem you used for enchanting it).

edit : Or whatever Maker16 said

Do i fill a soul gem by casting 'soul trap' then killing any enemy?

I'm pretty sure that the soul stone you use for your enchantment, as well as you skill/perks in enchantment have an impact on how powerful an enchantment you can give an item/how many uses it has before it must be recharged.

Yes, provided you have an empty soul gem that can hold the soul.

Yes, although i'm not sure if you have to trap the target before the killing blow. I use enchanted weapons with Soul Trap. Some need you to kill the target within a specific amount of seconds, but to my experience, as long you deal the finishing blow with the enchanted weapon you're fine. You'll see a purple glow coming off the target when you trap a soul. Different targets need different sized Gems though, and make sure you don't trap Lesser souls into too expensive Soul Gems. Unfortunately this is hard to control since the system just picks a random Gem to fill.

sweet, thanks. I will take down a Giant later and get his soul

You'll need at least a Common or Greater Soul Gem for that

Do you have to kill the enemy within the cast spell. In the blue circle?

There is also a slider while enchanting an item that can change the number of charges. When enchanting with soul trap for example the slider changes the time in wich the creature has to die. The shorter the time set, the more charges the weapon gets.