As you can read in the screenshot the entropedia integration can report loots back to entropedia. This is done anonymously, no avatar name or anything like that is sent.
As the log does not contain the mob that droped the actual loot EuHunter has to verify the loot data, this is done by checking the damage you did against the actual mob. For this verification you need to select the hunted mob and the maturity. The mobs hp and regeneration is taken from the mob list (fetched from entropedia). As this data is used for entropedias drop rates you have to confirm that you hunted these mobs alone and the other team member did not kill mobs (would mess up drop rate).
The tolerance for the verification is 5% +- 1.5 times your average damage.
Form a team with a crafter or someone who is not out killing mobs.
Select the mob and maturity you will hunt.
Click the Set button -> the marker in the Header should turn green. If turns red you most likely have unchecked the Report loot to entropedia checkbox.
Do your run.
If Upload on save is selected the upload will start when you save the run. if not you have to click the Upload now button before you save/close the window! The circle next to the upload now button indicates if there is data that can be uploaded.