The thing is, your higher self is the "real" you and the part of you that is wondering about it, is the "unreal" you... and it does not truly matter what the unreal part of you feels. So there is no wrong way to speak to your Higher Self.
I would suggest giving yourself permission to imagine that you actually have a Higher Self. And then sitting quietly in a pleasant place, and calming yourself... looking at the world around you... noticing your senses... noticing your emotions...noticing all the thoughts which float by... but all with the underlying feeling that what is deeply truly you... is the One watching, not the things watched. Not even the ideas, emotions, sensations. They serve you, they are not you. This is sometimes called mindful meditation.
Then your "watching self" can say "yeah, I give myself permission to ask my Higher Self, whatever that is, to attune me to such-and-such a system. And let yourself receive the attunement, whether you feel anything or not. Remember the energy sensations people talk about, are not their "true" selves... just sensations.
Do you mean we can attune ourselves to any kind of energy system without the permission of the channel explorer?
So how do we know that the channel opener is allowing such a thing like, giving it for free? Maybe he is blocking to people who don't pay for it?
I am confused.
There are manuals which carry the energy "embedded" in them for one direct use. You are allowed to absorb the energy from them, on the website. But if you take a copy of the manual, you lose the embedded permission and it becomes just a regular manual.
There are systems which declare themselves to be "self-attuning" which is what the original question concerned.
Yes, you certainly may attune yourself to any energy, if you are talented at self-attunement. But it will not be the "official" form of the energy and it would be wrong to resell it. And you will not have a teacher lineage. And if you try to sell reiki attunements you have not taken down politely, you will get a bad reputation.
If you are poor and starting out, its a good idea to reach out to inspiration and make your own energy healing systems, and write your own manual.