Still Main quest related.
*** Spoiler - click to reveal ***Alduin's Bane
Now that you possess the Elder Scroll, return to the time wound on top of Throat of the World. Read the scroll inside the wound to witness the demise of Alduin in a previous era. All you got to do is watch the scene and you will learn the Dragonrend shout. When back to reality, Alduin will attack you and Paarthunax. Face it as you would an usual dragon, the only difference being you have to use Dragonrend top force him to land so you can lay in some serious damage. You will eventually prevail, but Alduin flies away.
Season Unending
Talk to one of your usual counselors and you will have to visit Jarl Balgruuf to convince him to use Dragonsreach to capture a dragon. He will refuse to help while the civil war is going on. So you ask the Greybeards to organize a peace treaty within their walls. Go give their invitations to General Tulius and Ulfric Stormcloak, than regress to High Hrothgar to discuss the future of Skyrim. Deal with Elenwen as you please, make the Markarth/Riften exchange, than agree to the compensating demands of the counterparts so everyone leaves 'happy'. The treaty is than agreed and the quest complete.
*Optional quest: if you completed the civil war questline before ending Alduin's Bane, than Skyrim is reunited/liberated and this treaty has no reason to exist, so the quest will simply be skipped.
The Fallen
At the end of the truce Esbern will reveal the words of power to call Odahviing, so you can lure it into Dragonsreach great Porch. Tell Balgruuf you're ready and use your newly learned Thu'um to call the dragon. Take the fight, but know it can't be actually killed (its health will replenish whenever drained). What you have to do is to lure it under the trap in the enclosed area. When captured, bargain with the dragon for a trip to Skuldafn in exchange for its freedom.