To unlock new artes in Tales of Arise, you will need to earn SP from killing enemies or completing quests and leveling up. When you earn enough SP, you can use these points to unlock new artes to use in combat.
You can unlock more titles as you progress in the game by performing various actions. Unlocking titles will unlock new skill trees with new artes. Using SP points will allow you to unlock both skills and new arte abilities on these title skill trees.
You can also unlock brand new artes by using one of the arte variations such as Blast Strike and Gun Strike. The more you use these abilities, you will eventually unlock more abilities of the same type.
That said, the key to unlocking new artes this way is to assign your characters a few abilities via the artes tab in the main menu so that they will focus on using those skills more.
The more they use them and get kills, the more they will potentially earn more abilities of that same time and raise their proficiency with that skill.
If you control your companions during battles, you can also help get new skills by using their artes. Manual control of companions will also allow you to assign skills similar to Alphen.
Check out some of our other Tales of Arise guides!