Hi Celine thanks for posting in the Lucid Community! Do you have your logo in the form of an image file? If so I recommend uploading your image to Lucidchart by clicking on the Image icon in the Shapes Panel then selecting the Image upload option.

Alternatively you can simply drag and drop the image file onto your canvas. I've shown an example of this with Lucid's logo on a sample org chart below:

For more information on using images on your canvas I recommend this Shape Libraries article from the Lucidchart Help Center. Please let me know if you have additional questions!