Attuning to items can be attempted without synchronicity through the use of the Arcane Lore skill. This is done by spending an extended rest in contact with the item normally. More rare and powerful magic items have variously odd and epic needs for attunement like 'under the full moon', or 'drenched in the blood of a demon', etc.
If the character does not possess that skill they may use a base statistic roll related to the source of the magic item as follows:
Arcane: Cha, Con, or Int
Primal: Cha or Wis
(If this isn't clear that is d20 + statistic modifier)
Rolls and modifiers:
Base DC for a 1 power item: 17
Base DC for a multi-power or propertied 1 power item: 22
Base DC for multi-powered propertied items: 27
-3 for single use (non permanent) magic items like many scrolls, potions, and gems.
+3 for every level of the item above the level of the character,
-1 for every level of the item below the level of the character,
+-1 for each hit point of blood magic used (requires that feat)
-2 for performing the ritual inside a mage circle
-2 for performing the ritual on a ley line
-2 for performing the ritual inside a constructed focus (magical academy)
+2 for attempting to attune to an item from a source your class cannot normally do magic in.
+1 for every point the former user (if still attuned) made their attunement roll by (so track your rolls)
These are not all the modifiers just the most commonly known ones.
Failed rolls: You may fail an attunement roll with any given item up to a number of times equal to the score of your highest relevant modifier. Once that happens you cannot attune the item until your statistic is raised enough to get you another modifier point.
Fail by 5 is just failure and the item is not attuned.
Fail by more is a fumble with a corresponding magical event.
What events can happen: Unknown!
Example: Kitty Bumpo Rogue Cha 16 and Mylar Chez wizard int 20 are vying for a magical item. They have just killed Imperio the Rogue, the former owner. Each character is level 1 and the item is an arcane magical hat level 4 that is a 1 power propertied item.
DC = Base DC (22) + level (9) = 31
Kitty is a rogue but she multi-classed into wizard and thus has an arcane class. She does not possess Arcane Lore and her int is only 12 so her best bet is cha at +3. She doesnt know rituals and cant make her own circle and Mylar is an ass and will not help her out (hard to make a circle for someone else anyway). So:
Kitty's roll is 1d20+3 and she cannot attune this item.
Mylar builds a circle and has located a ley line. His arcane lore roll is 12.
Mylar's roll is thus 1d20+16 and it is remotely possible he can attune the item (30%).
Mylar is aware that Kitty cannot make the roll as all of t he above knowledge is only technically available to those with trained arcane lore. He tells her but she persists anyway because she is like that.
Kitty goes first and rolls a 3+3 = 6 Fail! She rolls and gets no event.
Mylar rolls and gets a 3+16 = 19 Fail! He rolls and gets an event. He is afflicted with a magical disease that makes his hair fall out over the next three days.
Kitty goes next and rolls 17+3 = 20 Fail! She rolls and gets an event. The event somehow attunes her to the item anyway and in fact fuses it (the hat) to her head permanently.
Playing with magic can be funny and dangerous!