We let her out for longer periods each day once our kitten was over her op. I kept her in the garden at first as she's quite a small kitty (had to rescue from up the tree a few times!!). She just found her confidence slowly and we gave her a safe route in and out of the garden by lowering one of the fence panels . The first time over the fence was She's always in overnight.
We don't have a collar for her but she's microchipped.