Hey mate ...
Follow those instructions .. Easy, and will save you on heating bills!

1. Top up the pressure from a flexible "fill loop" This is maybe already fitted between mains water and system .. or dangling ... or not one fitted at all!
Usually looks like a braided stainless steel hose. It has a 1/4 turn slotted valve at each end, usually. open slowly after connecting to the mains, and watch the system pressure rise to 2bar. Then follow what I said about bleeding, balancing, etc!

2. The lockshields will usually be on the outlet ends of rads, except some Thermo valves can be fitted as an inlet OR outlet controller. Thats usually the dear liquid filled head type with chrome caps. So you cant do much wrong.

Only time you should be careful is with a system that has no bypasss valve (NOT a combi) You should make sure that circulation CANNOT be completely stopped.
This is why some bathroom rads that you see have a lockshield at both ends

Back later mate