Where in TurboTax Businees do I enter partner share of AGI for K-1?

a partner's 1040 AGI is never reported on a K-1 

20AG is for their share of the partnership's gross receipts(should be automatic)  to determine if under section 448(c) thy must use the accrual method of accounting . The applicability of this code section is for each partner r to determine

Code AG. Gross receipts for section 448(c).
Regulations section 1.163(j)-2(d)(2)(iii) requires that
partners in a partnership include a share of partnership
gross receipts in proportion to their share of gross income
under section 703 (unless the partnership is treated as
one person under the aggregation rules of section 448(c)).
Partnerships with current year gross receipts (defined in
Regulations section 1.448-1T(f)(2)(iv)) greater than $5
million are required to report to their partners their
distributive shares of current year gross receipts, as well
as their distributive shares of gross receipts for the 3
immediately preceding tax years. If a partnership and a
partner are treated as a single employer under the section
448(c) aggregation rules, and the partnership has current
year gross receipts greater than $5 million, then the
partnership should also report its total current year gross
receipts, as well as its total gross receipts for the 3
immediately preceding tax years, to that partner. See
IRS.gov/newsroom/faqs-regarding-the-aggregation-rules
under-section-448c2–that-apply-to-the-section-163j
small-business-exemption.