If you just want to get online on Siemens you open the file you want,click "baustine" or blocks,choose any fb or function block,double click and you get the program in front of you.
Click the "spectacles" icon and,if connected properly you get online,there should be a green bar moving left to right at the bottom of the screen and everything "active" goes green,ie inputs into the function blocks etc.
Thats as basic as I can explain it but its really easy to use,much better than s5 but IMO not as good as logix although each to their own.
Right click on any function ie A 80.1 and a box opens offering you to "go to location",from there you can type anything you want into the search box and look for it,no matter what fc it occurs in.
Not sure if it's just relevant to the program's where I work but the = sign next to it means it's where it's "generated" from,ie what brings it on.
You can use a vat table or variable table to monitor several functions at once and even modify values from here.
I enjoy using it anyway,but like most things it's only as good as the person who programmed it.