Aracely, you can either submit an updated package and explain that the taxpayer need to update the financial package, or wait for the IRS Offer specialist to contact you. First of all are they still an offer candidate wit the additional info/assets? If so I would actually be proactive and submit an updated package and explain that you already submitted the package on ____ date but the client, in reviewing it, realized they missed items and are now submitting an updated package.
If they are no longer an Offer candidate then I would send a letter requesting to withdraw it.