The frequencies provided are output frequencies. That's what you want almost all the time when you're scanning - the output frequencies are at a much higher power and you'll hear both sides of the conversation. Listening to the input frequencies is mostly useless, except in very specific cases.
Finding out which tone is to be used is done in a number of ways. Some people obtain it through getting lists from sources close to the action, so to speak (i.e. knowing someone who has the official info from the RCMP, or whatever service you're trying to listen to). Some people use what's called 'tone search', a feature available in a few scanners where it will find out what tone is being used on a specific frequency. (I don't know if the one you're looking at has tone search or not - sorry.) But the easiest thing for you to do would be to program all the RCMP channels in as seen in the channel listings on this web site's database. That way you'll have all the channels and both sets of tones already set up - so you're bound to hear whatever the local area is using.
If you program in 155.55 by itself with no tone setting, you'll hear stuff, for sure. You'll hear the channel known as B2. You might hear the channel known as B7 - if any detachments in your area are using it. You might hear "bleedover" from other services using frequencies "near" to 155.55, if the signal is overly strong. And you might get interference from things which generate a lot of RF (radio frequency) "noise" - like computers, television sets, the computers/mechanical parts of your car, etc.
If you program in 155.55 and put in a tone setting of 123.0, you will hear ONLY transmissions that carry that tone setting. Nothing else will come through, on that channel in your scanner. If you program another channel in your scanner as 155.55 and a tone of 131.8, you will hear ONLY transmissions that have tone 131.8 on them - even if other transmissions have a tone of 123.0. Those transmissions would be heard if your scanner stops on the other channel (the first one we programmed in this paragraph).
There's no point in programming tone settings other than 123.0 and 131.8 in terms of RCMP usage - they only use those two for the detachment channels.