The following chart summarises the rule.
If Zi Wei Star 紫微 is at Yin 寅 or Shen 申 Palace,
Tian Fu Star 天府 will reside in the same palace as Zi Wei Star.
If Zi Wei Star is at Mao 卯 palace, Tian Fu Star will be at Chou 丑.
Likewise, if Zi Wei Star is at Chou 丑, Tian Fu star will be at Mao 卯.
If Zi Wei Star is at Si 巳 or Hai 亥 palace,
Tian Fu Star will be at Hai 亥 and Si 巳 respectively.
You can double-check the position of Tian Fu Star here.
By the end of Step 8, you would have successfully charted 7 Major Stars.
