Joining the Legion

Information
This quest belongs to The Imperial Legion quest line.

Quick Walkthrough

 * 1) Go to Solitude and talk to General Tullius.
 * 2) Speak with Legate Rikke and accept her test.
 * 3) Clear out Fort Hraggstad and report back to Legate Rikke.
 * 4) Talk to General Tullius and take The Oath.

Detailed Walkthrough
In the beginning of the game when you escape Helgen, make sure you follow the legionnaire named Hadvar. After the two of you get out of the cave, Hadvar will tell you to join the Imperial Legion in Solitude.

Make your way to Whiterun (the closest city) and, just outside of the city by the stables, find the carriage driver Bjorlam and pay to be taken to Solitude, as you can't fast travel to cities you haven't already been to. When you get to Solitude, make your way to the castle in the upper part of the city and enter through the main entrance.

Talk to General Tullius, who will direct you to Legate Rikke in the same room. Speak with her and accept her test of clearing out Fort Hraggstad, which has been run over by bandits.

Follow the quest marker to find the fort. After clearing the fort, report back to Rikke who will tell you to speak with Tullius about The Oath. Take The Oath and you have officially joined the Imperial Legion.