There are 2 ways to classify an asset into a Classification Scheme
Via Asset Info > Classification
1. Select an Asset Classification Scheme
2. Select a portfolio on the top right panel
3. The portfolio assets will be shown on the bottom panel. Double click on an asset to classify the asset.
4. Classify asset by selecting from the dropdown list.
Via Holdings Page
1. Select a "Major Grouping" on the bottom of the Holdings page.
2. Right click on an asset and you can choose to classify or declassify it.