I downloaded it to a USB and used Rufus to make it an ISO. I put it in another computer and when I choose install, there are no options to download the OS, then it crashes and opens the tryal version.
The question is not clear but I assume that you downloaded elementary OS and wrote a bootable USB using Rufus.
In the process Rufus might have asked you two option to write in
dd.Use both and. Finally check the USB by ticking the check option in Rufus.
I think the iso image might be corrupted due to incomplete download.