Questions about formulas and buying items from trainers

[Lascivious Goat]

New to Horizons (playing 7 day trial) so I'm a bit lost about how some things work in this game. I want to buy Beginner formulas (for blacksmithy) and I've done so with the formulator machines in New Rachival. But I've read that I can also buy formulas off Trainers. Thing is, the Trainers don't seem to have any forms when I offer them a Lore token in the trade window. How exactly do I go about buying forms off Trainers?

And this leads to my second question: how does the trade window work. When I browse the Trainers for stuff to buy off them they never seem to have anything for sale. I've mucked about with the filters and searching for stuff 3 days old etc, but come up blank. Would appreciate advice about using the trade window.

[Oz]

Don't bother with a time constraint, the formulas are always on the trainers. Instead make sure everything is off on filters except able to use. Then look on the left tab for thier items there should be quite a few. The will sell forms from 5c up. What 5c means is 5imperial lore tokens.
Choose the forms you want by double clicking, then look at how much the total is. Go to the left tab "your items" and drag over the correct amount of lore tokens. When the total cost is equal to 0 accept the trade.

Make sure you arent hitting the sell only button, and that your filters arent filtering out forms, that you are using a blacksmith traininer to buy from.