Text-editor

To modify Halvor you should have a text editor. You can use any editor (e.g. Atom, Sublime Text, etc.).

FTP Client

To publish your website you will need transfer files to remote server of your hosting. It's very important to understand that you must either have your own server space or use someone else's. The server space can be purchased at many different places around the Internet. You need somewhere to put the files that you purchased so others can find them online.

To transfer your files to server you can use different FTP clients (e.g. FileZilla). How to upload files to server with FileZilla you can read here. You should upload the contents of an archive to root directory.