An assembly, installation package and method for installing a wind turbine tower. The assembly (139) comprises an installation unit (114) having unit guides (140), each configured to engage a corresponding engagement guide (130) adjacent to an upper inner edge of the tower section (110) to guide the assembly while it is lowered into the tower section. The assembly also includes a yoke (136) releasably connected to the installation unit and comprising yoke guides (146), each configured to engage a corresponding engagement guide (130) adjacent to the upper inner edge of the tower section to guide the assembly while it is lowered into the tower section (110). The assembly (139) is configured such that at least one of the unit guides (140) and/or the yoke guides (146) is or are substantially continuously engaged with the engagement guides (130) from when the assembly (139) enters the tower section (110) until the assembly reaches its installation position within the tower section.