If you populate a card that is a 1/1 and there is a enchantment that give all creatures 3+3 the copy of the card that is populate is a 1/1 plus the enchantment or is a 8/8???
When you copy a card (or a token) you copy the base stats. The original token is a 1/1 so your new token will be a 1/1. Then, it will be affected by any continuous effects from enchantments (such as Glorious Anthem) at that point.
The token will not have the +3/+3 effect from the enchantment. In general, when an object becomes a copy of another object, the only effects that are copied are other copy effects (layer 1 [C.R. 613.1a]) as well as characteristic changes from "'as ... enters the battlefield' and 'as ... is turned face up' abilities that set power and toughness (and may also set additional characteristics)" (C.R. 706.2). (The closest card to the enchantment you have in mind is Crucible of Fire.)
Populate