From the Settings Page, navigate to Reporting Settings → Target Allocations.

From here, you can Create a new Target Allocation by clicking the Create button on the top right. You can choose from default or custom asset classes on the dropdown menu. To add custom asset classes, see this article.

You can also edit an existing allocation by selecting the name of the allocation you'd like to adjust.

To learn more about Target Allocation Tolerances, see our article here.