Hi, can someone tell me how can upload pictures in ArcGis Online maps?
Stefan,
it all depends on where your photos are stored, the following blog shows you how to add photos from Flickr:
Using Flickr photos in the hosted map tour story map | ArcGIS Blog
and facebook:
Using Facebook photos in the hosted map tour story map | ArcGIS Blog
from a csv:
Using the Storytelling Playlist template | ArcGIS Blog
from dropbox:
Using Dropbox files in ArcGIS Online web maps | ArcGIS Blog
storing files in arcgis online: