In the Security & Compliance Center (protection.office.com), you can select Alerts | View alerts from the left navigation pane to view, filter, and resolve alerts:
To view more detail on an alert, check the box to its left. This opens a pane with more detail and the option to resolve it as seen in the screenshot that follows:
If you select Resolve on an alert, you're able to modify its status and add additional comments. For the status drop-down list, you can choose from the following to help track the status of ...