You can assign which channels a member group can edit using the channel assignment section of the member groups permissions screen. This will restrict the member groups access for posting/editing both in the CP and via stand alone entry forms.
You can also then use the Channel Posting and Editing Privileges controls to determine whether CP users can edit/delete their own entries and view/edit/delete those of others.
However, it is not possible to make a channel accessible as "read only" for a member group while allowing them editing permissions on another (as I think you are looking to do) using native functionality. Once you set ""Can edit entries authored by others" for a member group they will have the ability to edit entries in all channels they have access to.
That said, you could still get very close to what you want by either using a custom status group and setting permissions so that editors cannot make entries live even if they can edit them, or by using a custom extension to prevent members of your editor group from submitting entries in your chosen channel. The hook you would want for this is entry_submission_start