The TV remote - those are just selectors so you can see whatever device you want. They don't impact whether or not something is recorded, just visually seeing it. So if you hook up the Freeview box to AV1 then you need to be on AV1 to watch it. And if you hook up the DVD recorder to AV2 then you need to be on AV2 to watch it. Just look at the back of the TV for how the ports are labelled.
To figure out whether or not you need to be watching a program in order to record it on the DVD recorder you can just do a simple test. Send the Freeview feed into the DVD recorder (just connect matching cable types, if both have SCART use that, if both have other options, use that). Then run the DVD recorder out the TV.
Now, using the DVD recorder remote, try to change the channel. If the DVD recorder can scan through all the channels, then you can program it to record something you are not watching. But if it goes to static on any channel except for 3, that means the Freeview box is dictating the channel. If the Freeview box dictates the channel, then yes you have to watch whatever you record.
The other description above would work as well. But you're still feeding the DVD recorder from the Freeview box. So whether or not you need to be watching what you record is still going to depend on whether or not the DVD Recorder and scan channels on its own or is dependent on the Freeview box. If it can scan channels on his own, the method above, where you use the Freeview box to separately feed both TV and DVD recorder would actually work well.
As for the manual issue, have you tried Googling for an online manual for the DVD recorder then? Just pick it up and look at the front and back for a model number.
But in the above description, he asks you to put the Recorder onto L2 (or such). The DVD Recorder remote should have some kind of button that says TV/Video or AV Select or Input, or something like that. It will allow you to cycle through the various inputs. So just make sure its fed into the TV and the TV is on the right input for the DVD recorder. Then cycle through the DVD recorder options until you see a signal on the TV (if you have to do this without the manual that is).