Cannot load demo themes

I am annoyed that so many people have this issue and yet you wont post one proper solution to it for everyone to see. I have searched all day to get these 3 errors sorted. I have got rid of all except “max_input_time should be at least 300 Seconds”. When I put the entry in .htaccess the entire site crashed. I am technical so can fix these issues myself but I need to know the correct parameter and which file to put it in and where it resides. I need the photography theme ASAP and am fed up with wasting time after I went to the trouble of purchasing this theme. I had less trouble with the free ones.