you can't without a Power of Attorney. this is a legal procedure. the means to get a POA varies from state to state. see a lawyer but this will probably take time. the POA would need to be attached and the entire return paper filed
or
you could e-file the return without signature and then prepare form 8453 and attach the POA which has the following filing requirements if you e-file
If you are filing your tax return using an online provider (ie Turbotax), mail Form 8453 with the POA to the IRS within 3 business days after you have received acknowledgment from your intermediate service provider and/or transmitter that the IRS has accepted your electronically filed tax return. If you don’t receive an acknowledgment, you must contact your intermediate service provider and/or transmitter. Mail to:
Internal Revenue Service
Attn: Shipping and Receiving, 0254
Receipt and Control Branch
Austin, TX 73344-0254
