Chemistry Programming for CREST Award

Hi, I am 19 years old and trying to complete my CREST Award relating to computational chemistry and modelling etc. (for University - I took a gap year and am no longer in college so have no teachers to ask for help). However, I tried downloading some free software on my MacBook and I am really struggling with it and I can't seem to find any help anywhere. If anyone has any good suggestions on free software I can download and use for my project (I can't do it without) and can help me with fully downloading it to my laptop I would be unbelievably grateful. Thank you so much <3