So that could be by upgrading runes already in an item or crafting unset runes in a device with reagents or multiples of the same rune combining to ‘upgrade’ the rune.
Blizzard also appears to be using the same names and some of the visual representations of the rune symbols as seen in Diablo 2. It’s unclear if all the 33 different runes from Diablo 2 will be added to Diablo IV.
Some of the runes have been confirmed already but note, the socketed properties in Diablo IV are different from the properties in Diablo 2. Below is a list of all the expected runes based on Diablo 2. The list shows confirmed runes for Diablo IV and their new properties.