Vinteum spawns in the same areas iron does in large veins. You'll need some of this to continue.

Smelt the vinteum ore in a furnace or blast furnace to get vinteum dust.

Combine that with iron to make vinteum coated iron.

Then smelt that to make a vinteum bar.  You will need 5-10 of these so make extra.

New buildings spawn in villages with spellmonger villagers in them.

Trade 5-10 vinteum bars to get the Codex Arcana.  Read the book and it will guide you from there!

There will be methods to start the mod in the future that don't require exploration or a village.

The spellmonger's job block is the Runeforge.  The needed recipes to make that are shown below.