Lets first take a look at the minimum system requirements to install oVirt 3.5 Manager:
A dual core CPU
4 GB RAM
25 GB free space
1 GiB NIC
Fedora 20
Now we will check the actual requirements for installing oVirt 3.5 Manager:
A quad core or better CPU
16 GB of system RAM to start with, and an option to increase as per the need
50 GB free space, ideally on LVM
1 GiB NIC
Fedora 20
We assume that you already have a Fedora 20 server installed. If you need help to install Fedora 20, follow the instructions at https://docs.fedoraproject.org/en-US/Fedora/20/html/Installation_Guide/index.html
It is also important that you dedicate this server, exclusively, to an oVirt engine. This will make the installation less complicated and error free.