Select an option in the list to the left to change it. Information about the selected option appear in the panel on the right.
Under the description is a section named Target, in which you can select from different choices. A choice is selected by using the check box next to it.
Note - Some options allow you to make different choices for different contaminants. For example, the Man model let you specify if a specific contaminant enters the body via the GI tract or via the liver. For these options there is a drop-down menu just below the Target label where you select for which contaminant you want the choice. Use the default item in the list if you want to apply the same choice to all contaminants.