How to remove files in recovery mode to finish installing the new OS?

So I tried installing the new OS but unfortunately I was not paying attention and my battery died in the middle of it. I cannot boot up my macbook air at all, I go into recovery mode to try to install it from there but since it did not finish installing from the first time, it took up some space on my hard drive and I apparently need an additional 1.8 GB more to actually finish up installing the new OS. So I'm stuck in recovery mode and trying to figure out how to remove some files that I do not need on my hard drive, can someone please show me how? I tried figuring it out in terminal but I really am not familiar with the syntax used and can't seem to change my working directory....

I've searched all over the web but have not found my answer, I do not have a backup of my mac (I know, very smart of me) so I really do not want to wipe it clean... Please, someone help. I'm desperate!!!

Thank you in advance!