I bought an iPhone 11 and got a usb c to lightning how do I charge my phone?

If you have an older USB power adapter and cable from a previous iPhone or iPad, you can use that; or if you have a USB-C power adapter or computer with a USB-C port you can use that with the new cable or you can purchase a USB-C power adapter such as: Buy 20W USB-C Power Adapter - Apple

Also see the following from Buy iPhone 11 - Apple

As part of our efforts to reach our environmental goals, iPhone 11 does not include a power adapter or EarPods. Included in the box is a USB‑C to Lightning cable that supports fast charging and is compatible with USB‑C power adapters and computer ports.

We encourage you to re‑use your current USB‑A to Lightning cables, power adapters, and headphones which are compatible with this iPhone. But if you need any new Apple power adapters or headphones, they are available for purchase.