Blessing is the act of empowering some form of construct through the power of an entity, or particular energy.
There are many ways that you can bless a construct using your craft and/or practice. Doing so will allow that construct to be in the favor of, or power of the specific entity, or energy of your choosing, so that it can intern take on some of the power of that entity, or energy. This will make the construct stronger, and more connected to the entity, or energy.
Blessing a construct is a great way of dedicating it to a specific energy, or entity, so that it can watch over, and be a part of that constructs existence. Constructs can also become blessed by entities by asks the entities bless that construct. You may also have to do some form of a ritual in order to dedicate that construct to that entity. In this ritual you might try bringing in things that the entity is connected to in order to bring more of their energies into your blessing ritual. The things that you would need to bring into your ritual may be things such as prayers, chants, holy books, crystals, herbs, symbols, oils, and anything else that has been dedicated to that entity already, among many other things. This can be done with deities, angels, demons, guides, and even ancestors among many other things. This will allow you, and the construct to work closer with that entity to help further your practice, and craft.
Some entities may have specific ways that they will want you to go about, in order to get their blessing. This may be some sort of already previously established ritual from a tradition, custom, culture, or lore that the entity may be a part of.
Alternatively, to get the blessing of something that is more an energetic construct than an entity, you would need to do something like finding a way to push the energies that you want to use to bless with, into the construct that you are blessing. This would be like invoking fire energy, and then pushing that fire energy into the object both blessing, and empowering it with the energy, and the essence of fire.
You can even bless constructs using your own energy by putting your energy into them, and empowering them by using energy manipulation primarily a technique like the one I explained in this article: pushing energy. The act of blessing can be a very influential part of our craft if we allow it to be, and can greatly empower our rituals, and practice.