Try "isolde restrain torsions sel" and/or "isolde restrain distances sel". You can also do this via the "Reference Models" section of the ISOLDE GUI (just choose "(self)" in the Reference model drop-down menu), but the commands give you more flexibility. When you're doing big rearrangements like this, it is also usually preferable to use the "tug selection" mouse mode (far right of the ISOLDE ribbon menu while you're running a simulation) rather than the default "tug atom".