In Elden Ring, you’ll find a wide range of characters that will share their plight with you, most of these will have Quests that span multiple locations. This page will detail where you can find Renna and complete her Questline.
First Meeting - Church of Elleh
Your first meeting with Renna can actually be an easy one to miss, and it’s important you don’t because you’ll obtain the useful Spirit Calling Bell in the process. Once you meet Melina, the maiden, for the first time at your third Site of Grace in the field, rest until it’s night. At that point, travel back to the Church of Elleh and you’ll encounter her sitting on the ruins.
There’s not much you can do for now, but simply speaking to her and confirming that you have use of the Spectral Steed, Torrent will see her hand over the Spirit Calling Bell. This will allow you to make use of the Ashes you find throughout the Lands Between and summon Spirits to aid you in challenging battles.
Following this first, brief, meeting with Renna, you won’t encounter her again until much later in your adventure where you will officially begin her Quest.
Second Meeting - Liurnia of the Lakes
You’ll eventually meet up again with Renna once you defeat the boss of Caria Manor and gain access to the Three Sisters sub-region. Inside here, you’ll find Ranni’s Rise to the west where you can speak with Ranni the Witch, the true identity of Renna. This begins an important game-wide Quest, and you’ll find more details on Ranni the Witch’s page.