Ok here goes......

1. Ensure you have:
New Gasket
Sealant for Gasket/half moon seals (i use Blue hylomar)
New Half moon seals (worth changing as they are cheap, but not essential)
Allen key/socket for removing rocker cover

2. Undo all the bolts of the rocker cover

3. lift off cover

4. ensure any traces of old gasket are removed from both cover and head, pay close attention to around the half moon seals.

5. wipe down with clean cloth to remove any residual oil on both cover and head around contact surfaces

6. lay gasket in place on head, and fit half moon seals with a little bit of sealant to hold then in, and a little bit at the ends where they sit on top of the gasket

7. fit cover

8. torque down to specified torque......

Done