Start by checking out the telerik ASP documentation on the tree control.
There are several examples.
Your tree structure would look something like this:
<telerik:RadTreeView ID="RadTreeView1" runat="server" Height="250px" Width="100%"
EnableDragAndDrop="true" OnNodeClick="RadTreeView1_NodeClick" OnNodeCollapse="RadTreeView1_NodeCollapse"
OnNodeExpand="RadTreeView1_NodeExpand" OnNodeDrop="RadTreeView1_NodeDrop" Style="border: 1px solid #CBE7F5;">
<Nodes>
<telerik:RadTreeNode Text="Accessories" ExpandMode="ServerSide" Expanded="true">
<Nodes>
<!-- add Accessories nodes here -->
</Nodes>
</telerik:RadTreeNode>
<telerik:RadTreeNode Text="Awards" ExpandMode="ServerSide">
<Nodes>
<!-- add Awards nodes here -->
</Nodes>
</telerik:RadTreeNode>
<telerik:RadTreeNode Text="FIAT" ExpandMode="ServerSide">
<Nodes>
<telerik:RadTreeNode Text="2014" ExpandMode="ServerSide">
<telerik:RadTreeNode Text="500" ExpandMode="ServerSide">
</telerik:RadTreeNode>
<telerik:RadTreeNode Text="500c" ExpandMode="ServerSide">
</telerik:RadTreeNode>
</telerik:RadTreeNode>
<telerik:RadTreeNode Text="2014" ExpandMode="ServerSide">
</telerik:RadTreeNode>
</Nodes>
</telerik:RadTreeNode>
<telerik:RadTreeNode Text="Technology" ExpandMode="ServerSide">
<Nodes>
<!-- add Technology nodes here -->
</Nodes>
</telerik:RadTreeNode>
<telerik:RadTreeNode Text="Warranty" ExpandMode="ServerSide">
<Nodes>
<!-- add Warranty nodes here -->
</Nodes>
</telerik:RadTreeNode>
</telerik:RadTreeView>