As a wizard, with your DM’s approval, you can gain this free feat at 1st level.

• When you find a wizard spell of zero level, you can add it to your spellbook if it is of a spell level you can prepare and if you can spare the time to decipher and copy it. For each level of the spell, the process takes 1 hour and costs 25 gp. Additionally, you prepare the list of zero level wizard spells that are available for you to cast. To do so, choose a number of zero level wizard spells from your spellbook equal to your Cantrips Known on the Wizard table.
• As a savant in your chosen school of magic, you have begone to unlock the secrets of spells not normally known to wizards. At 2nd level when you select an Arcane Tradition that also grants a school of magic “Savant” feature you can add spells of your chosen school to your spellbook. The gold and time you must spend to copy these spells into your spellbook is doubled. When you find a spell of zero level or higher that is of your school, you can add it to your spellbook if it is of a spell level you can prepare and if you can spare the time to decipher and copy it. You must have your DM’s approval to add the spell to your spellbook.

For example, if you’re a 3rd-level school of evocation wizard, with the Evocation Savant feature, and you have a Moonbeam spell scroll, with your DM’s permission, you can add the spell to your spellbook. The process to add the spell takes 4 hours and costs 100 gp. Since the Evocation Savant feature halves, the time and gold cost you spend to add evocation spells to your spellbook, you are spending the same amount of time and gold to add Moonbeam which is not on the wizard spell list, as you would to add a spell of 2nd level from any school other than evocation.