Using 2x M5x8mm screws secure an internal corner clamp into the channel next to the Y linear rail at the front of the frame for both sides. The purpose of this is to use the corner as an alignment block.

Slide the Y MGN mount and using a compression clamp clamp the front mount to the front of the printer as seen in the picture. Do this for both Left and Right sides

Once both sides are clamped tighten the 6x M3x18 socket head screws, the 4x M3x30 button head screws and the 8x M5x8mm button head screws