Q: Software update

Hello

I went to the apple store as my computer wasn't working.  They said my hard drive was broken.  I went and brought a new hard drive and install it.

I then went on to install the software again.  When it came to the screen to install it, it said click on where you would like to save it to, nothing came up, to click on before I could press the install button.

Can anyone help please?

Thank you