Hey there
@Daisy Malfoy,
You can look at the map
here to find the location of various mob spawn areas. If you hover over a specific location with your cursor, you'll see coordinates in the bottom left corner of the map, which you can then follow in-game to get to the location.
As for your issue of not being able to kill mobs, you'll have to either get better gear or use professions items (potions and cooking items) to boost your stats temporarily. You can also always buy the ingredients on the marketplace (in Vertick Alley in London or by going to a specific players /housing if they are selling the items) to buy them from other players.
I hope this answers your questions and helps somewhat!
Regards,
Aurora