how to make feature should be only displayed to the admin?

If you want only administrators to view the features, set RequireSiteAdministrator="True" as shown in the below ElementManifest.XML file.

<Elements xmlns="http://schemas.microsoft.com/sharepoint/">
<CustomAction
Id="SiteActionsToolbar"
GroupId="SiteActions"
RequireSiteAdministrator="True"
Location="Microsoft.SharePoint.StandardMenu"
Sequence="10"
Title="Display Custom Pages"
Description="This links helps to display Custom Page"
ImageUrl="_layouts/SharePoint2/menuprofile.gif">
<UrlAction Url="_layouts/SimplePageCodeBehind.aspx"/>
</CustomAction>
</Elements>