From here on, you can talk to her whenever you like to get some practice in with the targets.
When you request some practice time, Angi will head down to the platform that looks out both at the archery targets and the mountainside over Falkreath. You will need to stand with her beside the bar that marks where to stand for the archery challenges she will give you.
After a bit of general archery advice- things like staying calm in a potentially exciting battlefield moment- she will tell you first to hit the middle target with a practice arrow. If you don't have any of these zero-damage arrows, she will give you ten if you should ask.
Hitting the target will give you a rank of Archery skill and prompt Angi to request that you hit the left target. This will again grant you an additional rank in Archery, and then the woman will have you move on to hitting the right target. After gaining a third rank in Archery, Angi will compliment you on a job well done and tell you to return if you ever want more practice.
Next time you talk to her, Angi will mention her brother- the two of them apparently went hunting with some frequency, and often needed to hit multiple deer before any could flee. To develop your skills, she wants you to hit all three of the nearest targets within an eight second span. She will count to three, and then start timing you when she says 'go'.
This takes a bit more focus, and good timing when drawing your bow- you can get a little leeway by having the Quick Shot perk or improve your aiming time and quality with Steady Hand, and Eagle Eye is virtually necessary for this particular feat of dexterity. On meeting the challenge, you will gain another rank of Archery skill and another compliment from Angi.
Angi's next challenge for you is to hit the far target- when hunting with your bow, you may not be able to get close and the one shot can be all you get. So this time you're to take your time and make sure you hit the target as perfectly as you can.