It will show stickers within the banner section like below and you can navigate by swiping the page.
Try to click on a sticker so then it will be sticked at the middle of the month view and you can drag it to where you want it to stick.
There are more categories of stickers, try to tap "folder icon" so then it will show more categories such as traditional, embodies...like below.
If you want to remove the stickers what you added, you can delete them by clicking the "X" mark at the left upper corner of the stickers.
Click the "Check mark" to go back to the month view.