𝓞 is extant here and can be read as either gat or got. Since the past participial gat clearly occurs in 𝓞 for nearby Alma 55:2 (“more power than what he hath gat”), the critical text will interpret the reading here in 𝓞 for Alma 47:5 as “he had gat the command”. In both Alma 47:5 and Alma 55:2, Oliver Cowdery copied the gat in 𝓞 as got in 𝓟. For discussion of other cases of gat versus got in the earliest text, see under Alma 10:32.
Here in Alma 47:5, the 1911 LDS edition replaced the past-participial form got with gotten. As discussed under 2 Nephi 31:19, either form is theoretically possible, but in actual fact the original Book of Mormon text has only gat and got, never gotten. So here in Alma 47:5, the form gotten is textually secondary. In this instance, the 1920 LDS edition restored the got of the earlier editions.
Summary: Restore in Alma 47:5 the past-participial form gat, the most probable reading (thus “and now he had gat the command”); there is some possibility that the verb form in 𝓞 can be interpreted as got (“and now he had got the command”).