It's totally simple.
I don't have XP here, so I hope you are using VX so I can explain you.
Name: Insert a name for your spell. (i.e. UBBER LEET FIRE WALL 2)
Icon: Cute image for your spell. (In this case, people burning.)
Description: Something that talks about your spell. (i.e. YOU GO WOOSH WITH FIRE AND PEOPLE GO WOSSHH)
Scope: It chooses who you want to use your spell on (burn bad guys, burn good guys, burn good dead guys, etc)
Occasion: If you can use your spell in battle only, in menuy only, both, or never (hum...)
MP Cost: The MP you need to use this awsome atack you have.
Hit Ratio: 100 means he will hit every time. 50 means he has a 1/2 chance to hit.
Speed: If someone uses an atack with speed = 0 and this spell is speed = 10, you will atack faster.
Animation: The little images that appear when you burn everone.
Call Common Event: Common events are like, if you have a common event stores and you want the atack to do that when used (i.e. you have a common event with a dialogue between characters... if that common event is used by a skill, that dialogue will occur time and time again)
Use Message: What appears when you do the attack.
Base Damage: If your attack should do 1 for a base (will do 1 every time) or 99999999 thousand everytime.
Variance: Determines how innacurate the damage is. For example, if it is 20 and your atack does 100 as base damage, it can go 20% below 100 or 20% above.
Attack F: How much it rellies on the character's attack.
Spirit F: How much it rellies on the character's spirit.
Physical Attack: If it's more a skill or a spell.
Damage to MP: You hit enemies MP so he doesn't have any to use an awsome skill.
Absorb Damage: If the damage is 200, your character will gain 200 HP.
Ignore Defense: Ignores the defense.
If you want to make healing spells, you simply take base damage and put the number there negative, so instead of taking HP, it gives HP.
The check boxes... for example, you tick your attack with the Element of Air. If the monster is weak to Air, it will do more damage, if he is made of air (lol) it will do less damage or none at all (you define that). State changes, if it puts the enemy dead, poisened, etc...