i tried to install it using Window -> Install New Software and then i gave the link http://subclipse.tigris.org/update_1.8.x
i tried restarting eclipse, restarting the computer. at first the installation goes without a hitch until it ran into this problem.
Error from Eclipse: Problem occurred
An error occurred while collecting items to be installed
session context was:(profile=epp.package.jee, phase=org.eclipse.equinox.internal.p2.engine.phases.Collect, operand=, action=).
Unable to read repository at http://subclipse.tigris.org/update_1.8.x/plugins/org.tigris.subversion.clientadapter.javahl.win64_1.7.10.jar.
Connection reset
The file is there, try it from browser. Must just be some kind of hiccup between Eclipse and the server or the network.
Note that Subclipse also provides zipped p2 repository you can download.