This Ayah (2:29) is explained in detail in Surat As-Sajdah where Allah said;
﴿قُلْ أَءِنَّكُمْ لَتَكْفُرُونَ بِالَّذِى خَلَقَ الاٌّرْضَ فِى يَوْمَيْنِ وَتَجْعَلُونَ لَهُ أَندَاداً ذَلِكَ رَبُّ الْعَـلَمِينَ - وَجَعَلَ فِيهَا رَوَاسِىَ مِن فَوْقِهَا وَبَـرَكَ فِيهَا وَقَدَّرَ فِيهَآ أَقْوَتَهَا فِى أَرْبَعَةِ أَيَّامٍ سَوَآءً لِّلسَّآئِلِينَ - ثُمَّ اسْتَوَى إِلَى السَّمَآءِ وَهِىَ دُخَانٌ فَقَالَ لَهَا وَلِلاٌّرْضِ ائْتِيَا طَوْعاً أَوْ كَرْهاً قَالَتَآ أَتَيْنَا طَآئِعِينَ - فَقَضَاهُنَّ سَبْعَ سَمَـوَتٍ فِى يَوْمَيْنِ وَأَوْحَى فِى كُلِّ سَمَآءٍ أَمْرَهَا وَزَيَّنَّا السَّمَآءَ الدُّنْيَا بِمَصَـبِيحَ وَحِفْظاً ذَلِكَ تَقْدِيرُ الْعَزِيزِ الْعَلِيمِ ﴾
(Say (O Muhammad ): "Do you verily disbelieve in Him Who created the earth in two Days And you set up rivals (in worship) with Him That is the Lord of all that exists. He placed therein (i.e. the earth) firm mountains from above it, and He blessed it, and measured therein its sustenance (for its dwellers) in four Days equal (i.e. all these four `days' were equal in the length of time) for all those who ask (about its creation). Then He Istawa ila the heaven when it was smoke, and said to it and to the earth: "Come both of you willingly or unwillingly.'' They both said: "We come willingly.'' Then He finished them (as) seven heavens in two Days and He made in each heaven its affair. And We adorned the nearest (lowest) heaven with lamps (stars) to be an adornment as well as to guard (from the devils by using them as missiles against the devils). Such is the decree of the Almighty, the Knower) (41:9-12).
These Ayat indicate that Allah started creation by creating earth, then He made heaven into seven heavens. This is how building usually starts, with the lower floors first and then the top floors, as the scholars of Tafsir reiterated, as we will come to know, Allah willing. Allah also said,
﴿أَءَنتُمْ أَشَدُّ خَلْقاً أَمِ السَّمَآءُ بَنَـهَا - رَفَعَ سَمْكَهَا فَسَوَّاهَا - وَأَغْطَشَ لَيْلَهَا وَأَخْرَجَ ضُحَـهَا - وَالاٌّرْضَ بَعْدَ ذَلِكَ دَحَـهَا - أَخْرَجَ مِنْهَا مَآءَهَا وَمَرْعَـهَا - وَالْجِبَالَ أَرْسَـهَا - مَتَـعاً لَّكُمْ وَلاًّنْعَـمِكُمْ ﴾
(Are you more difficult to create or is the heaven that He constructed He raised its height, and has perfected it. Its night He covers with darkness and its forenoon He brings out (with light). And the earth, after that, He spread it out. And brought forth therefrom its water and its pasture. And the mountains He has fixed firmly. (To be) a provision and benefit for you and your cattle) (79:27-33).
It is said that "Then'' in the Ayah (2:29) relates only to the order of reciting the information being given, it does not relate to the order that the events being mentioned took place, this was reported from Ibn `Abbas by `Ali bin Abi Talhah.