When you say “you need to insure them” do you mean insure them to drive your car or do they have cars of their own?
If the former they can be added to your policy as named drivers. If the latter they need to buy their own policies. Do not be tempted to “front” them (where you say you own the vehicle and they are additional drivers). This involves making a false declaration and insurers can and do revoke cover retrospectively should they find out. This will lead to possible prosecutions for No Insurance and (most importantly) no cover in the event of an accident.