1. Open Clan tab
2. Select "Edit crest"
3. Choose "Set crest"
4. Open your Lineage II System folder
5. Select the image for your clan crest
6. Double click it / Press "Registration"
*the image you want to use for your clan's crest has to be a BMP file, 16x12 pixel 256 color
**after you have a picture for your clan's crest (you can create one or find one on Google) and it has the required characteristics to be uploaded as a crest, put the image in your Lineage II System folder.
Lineage II Ertheia Official Server
