There are two types of FD mounts
FD/FL Breech-Mount (with a silver ring, you need to rotate the silver ring when attachment and removal), breech-lock mounts are identified by the silver ring
New-FD Bayonet Mount, bayonet mounts are identified by a red dot next to the lens release button

Here are the steps to install breech-mount version

1. Set your lens to smallest except for auto(bayonet mount only)
2. Rotating the Lock-Open ring of the adapter on the OPEN side
3. Line up the red dot with your lens and adapter ring(if yours is bayonet mount, just turn the adapter ring towards clockwise direction to make lens and adapter tight,then ignore the 4th step)
4. Turn your lens ring towards counterclockwise direction to make the adapter ring tight with your lens
5. Rotating the Lock-Open ring of the adapter on the LOCK side to engage the aperture closing pin

Operating the adapter

1. If you'd like to operate the lens aperture with the adapter; on your lens, set the aperture to the smallest opening and use the adapter ring
2. If you'd like to operate the lens aperture with the lens; place the adapter ring on the small aperture(Lock place) and control the aperture on the lens

1. Canon DSLR mount(Canon DSLRs, e.g. Rebel Series, 700D 650D 600D 550D 7D 60D 7D etc) is called EF, usually expressed by EOS, and Canon mirrorless camera(Canon EOS-M mirrorless cameras like M1 M2 M3) was usually expressed by EOS M
2. Nikon DSLR mount(Nikon DSLRs, e.g. D40 D70 D3100 D3200 D3300 D5100 D5200 D5100 D7100 etc) is called AI or F, usually expressed by Nikon/AI, and Nikon mirrorless camera(Nikon 1 series mirrorless cameras like N1 1 V1 V2 V3 S1 S2 J1 J2 J3 J4 AW1 ect) was usually expressed by Nikon1