Hi, I'm also a new player but hopefully I can help you out a bit.

It seems that, even for ants, you need to have quite a few skillpoints already in your combat skill of choice (best to choose 1 and powerlevel it, rather than doing them all) and you also need to get some Strength, Con, and some basic armour.
For a new player like you or me, doing all that is going to take a long time. But as far as I know, there is no other way around it. Simply put, naked newbies cannot kill anything, not even ants. x)
It is possible to use unbuilt fireplace constructions to trap a mob, allowing you to safely pelt it with slingshot rocks. However, you won't hit anything unless your marksman skill is >20 or so. By that time, you can probably survive attacking things head-on anyway!
Hope that helps a bit. I'd stick with catching rabbits and chickens for now, if I were you. That's easiest to do if you stand right next to the rabbit before you rightclick to catch it, or it'll run away and you won't be able to catch up.