Get the essence, get an elemental (earth, fire, air or water) tiara or talisman of the rune you wish to create and go to the certain mysterious ruins. You can find which mysterious ruins you want to...
Go to Candy, once she gives you a harvester, you then use this to collect runes and then you go back and find candy. Talk to her and ask for what ever you desire.You can ask for: rainy days sunny...
There is some at falador or "Port Sairiam" where becky is. I think there is some more if you can runecraft some it's very eaisier if you really runecraft. AND IN VARROCK
BY THE ANVILS SOUTH FROM...
The rune longsword is slower, but has a higher max hit by 1, but the rune scimitar is faster but has some unnecessary bonuses and is expensive, so the rune longsword is best.