how can I add a link to another website in the content of my web page

go to where you typed the address, highlight it and then click the hyperlink button in the little bar of icons in the text edit box. It look like a chain link.

a box will pop up - add the full domain name
eg. http:// www.yourdomain.com.au

in the Link URL field, click the insert button to save this. Now the text will be blue & have an underline. Click save