What software do i need to send my cv (uk)?

Is there any software that i can download free so that i can apply for jobs online? When i fill out online job applications there is always a section that you can click on to find the file that your cv is on so you can send it but i cant do that as it appears i dont have the correct software on my computer to do this. As far as im aware i need microsoft word but its very expensive. im not very computer literate so any help on this matter would be so helpful.