Below is a diagram showing where Cub Scouts place their badges on their blue uniform shirt top. From the wearer's left or right: The right pocket is for temporary patches, such as those earned on camp outs, pinewood derby, etc. They are hung from the button before the pocket is closed so the patch(es) is/are secured. On the wearer's left pocket are where the rank are placed. Per the updated policies, the first rank earned, regardless of when joining, is placed at the 12 o'clock position directly beneath the pocket flap, and centered. The second earned rank would be installed to the wearer's right, the third to the wearer's left and the fourth earned beneath. Installation is through sewing or using a badge holder (see below and here, $0.99+ tax, 2023). Sewing can be completed by yourself or through the scout shop (for a fee).
For Cub Scouts in grades 1 through 4, wearing the blue uniform shirt top:
For Cub Scouts in grade 5 (final year and earning their Arrow of Light), wearing the tan uniform shirt top, the rank of Webelo, if earned, is on the wearer's left pocket, centered. The rank of Arrow of Light, if earned, is placed below the wearer's left pocket. Note that the Arrow of Light is the only patch from Cub Scouts than can be worn when joining Troop 121: