Sounds like you are trying to install using the joomla installer.
This is no longer possible, see the big bold text at the release page:
https://github.com/joomla/joomla-cms/releases/tag/3.5.1

On Wed, Apr 6, 2016 at 8:54 AM, visualtribe notifications@github.com
wrote:

Steps to reproduce the issue

I am trying to update Joomla from 3.4.8 to 3.5. One of my sites for some
reason won't connect to the update package, so I downloaded version 3.5
(3.5.1 hadn't come out until today). When installing it comes back to me
saying that the xml file is missing. I opened the zip package and there is
no Joomla.xml file like there is in 3.4.7 and back as I have checked. I
downloaded version 3.5.1 and it too does not have the Joomla.xml file in
the update package. Can someone fix this please.
Expected result

Update package installs.
Actual result

Error now xml file. Can't install.
System information (as much as possible) Additional comments

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