pert:
You have two options:You can use the Uno as a dumb USB-TTL serial adapter by connecting the TX pin on your ATtiny85 to the pin marked TX on the Uno. You will need to make sure there is no sketch running on the Uno that will interfere with serial communication between the ATtiny85 and your computer.
You can run a sketch on the Uno that echos communication between a software serial port and Serial. For this you would need to connect the ATtiny85 to whatever software serial pin(s) you have defined in your sketch for the Uno. You can use File > Examples > 04.Communication > SerialPassthrough as an start for your sketch on the Uno but you need to modify it to use SoftwareSerial instead of hardware serial port Serial1 since Uno does not have Serial1.
I would actually prefer to just buy a dedicated USB-TTL serial adapter board rather than trying to use the Uno for this purpose. You can get them very cheap and they're a really useful tool.
Just make sure that the Arduino pin you defined for SoftwareSerial matches the physical pin you have the wire connected to.
I tested it now connecting the Tx attiny with the Uno Rx, but it showed strange characters on the monitor, so I tried with a usb-ttl that I have here and it worked perfectly, the bad thing is that I'll have to send the codes using the arduino and then test using or usb-ttl, but it works.