Javascript & Webforms

first i want to say, i hope someone can help, ive been to other forums & they ether didnt reply or was spitting hairs at me for been an amature at this. So i hope you guys are nice

Anyways, have my own website that loads another site in site an iframe & links on the left side of that page that loads the urls into the iframe. Now, some of those links loads a page with a form submition, for example Name & button for go or whatever. Now, i want just by clicking that url, to automatically put into that txt box a name/word of my own choosing instaid of clicking the link, loading the page & manually typing the words in.

So, to break it down.. 1 of my links goes to this site Sample website with a form box this has a form box with email box & password box at the bottom left. Now, u have to manually enter the email, password urself.. now lets say there was just 1 box to add a email in or name.. What i want to do is, just by clicking a link, it loads that page into the iframe & puts in the name/word of my chosing into the box for me, so all i have to do is click send or whatever.

Can anyone help? Im a learning html & know little javascript, i say little.. i ask people for help

thanks