The easiest would be that you search for the username in the web console search bar and open the user page of the user. It will list the assets to which the user has a relation.
If you want to do it in a report, you could create a report with parameters, like the following example:
Select Top 1000000 tblADusers.Userdomain,
tblADusers.Username,
tsysAssetRelationTypes.Name As Relation,
tblAssetUserRelations.StartDate As since,
tblAssets.AssetID,
tblAssets.AssetName
From tblADusers
Inner Join tblAssetUserRelations On tblADusers.Username =
tblAssetUserRelations.Username And tblADusers.Userdomain =
tblAssetUserRelations.Userdomain
Inner Join tblAssets On tblAssets.AssetID = tblAssetUserRelations.AssetID
Inner Join tsysAssetRelationTypes On tsysAssetRelationTypes.RelationTypeID =
tblAssetUserRelations.Type
Where tblADusers.Username = @username And tsysAssetRelationTypes.Name In
('used by', 'controlled by')
Order By tblAssets.Userdomain,
tblAssets.Username,
tblAssets.AssetName
After saving the report you will receive an error message. But you can go to the address bar of the browser and add something like the following at the end of the URL:
&@username=exampleuser