So now having our 3 parts with the right charm, we want to create the sword. Name it whatever you want and finally you'll have the basic sword.
After saving, our next step to make it have perfect stats by selecting Refine from Dojima's forge option. Select Make Stronger and keep selecting it until you are at max degradation (i/e 15/15).
Now Dojima has a random chance for each upgrade to have a high number or a low number, so to max things out quickly you can choice to restart the game every time he gives a low number saving each good upgrade but I prefer to aim for a total upgrade of 300 to 350 attack depending on degradation (14 to 15 max degradation for about 300, 16+ hard to say what you want to aim for but from 15 on each upgrade can be above 30 attack).
Either way unless your sword had 20 degradation (max possible) chances are you're a ways from the max of 500. From here we're going to be Recasting.
I'd 1st suggest selecting make harder until you have max durability from there we're selecting make stronger until again you hit the max attack. You'll gain up to 16 each time you recast your sword so expect each 100 attack you need to take 7-10 upgrades (especially if you accept a lesser number, which is fine!) so this requires a lot of ore, hope you saved some up