Freeview comes down an aerial not a dish and so you can't get it ion an old Sky box.
You can get some Free To Air (FTA) and Free to View (FTV) stations on an old Sly box. The former if the box does not have a Sky viewing card and the latter if it does.
You need to install, the dish pointing at a the Astra Group of satellites. How to is a big question and so I suggest that you do an Internet search because there are many sites on how to.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix satellite receivers.