you can't
reg 1.469-9(g)(3)
Filing a statement to make or revoke the election. A qualifying taxpayer makes the election to treat all interests in rental real estate as a single rental real estate activity by filing a statement with the taxpayer's original income tax return for the taxable year. This statement must contain a declaration that the taxpayer is a qualifying taxpayer for the taxable year and is making the election pursuant to section 469(c)(7)(A). The taxpayer may make this election for any taxable year in which section 469(c)(7) is applicable. A taxpayer may revoke the election only in the taxable year in which a material change in the taxpayer's facts and circumstances occurs or in a subsequent year in which the facts and circumstances remain materially changed from those in the taxable year for which the election was made. To revoke the election, the taxpayer must file a statement with the taxpayer's original income tax return for the year of revocation. This statement must contain a declaration that the taxpayer is revoking the election under section 469(c)(7)(A) and an explanation of the nature of the material change.
the statement is supposed to accompany the original return which would require you to file by mail. since the terminology refers to your original return, an amended return would not be appropriate.
