Mother can be snorted like a drug, it can be injected into the blood stream or it can be injected directly into the bone marrow that it's intended to modify. While the last option is the most effective, it's also the least comfortable by far, considered "excruciating, messy [and] dangerous" (regardless of whether the virus itself is authentic or not).
Bone marrow infected this way creates cells that are somewhere between a white blood cell and an embryonic neuron in what's best described as a single burst - these are called White Knights. They secrete cytokines that allow them to pass through the brain-blood barrier. Once they've entered the brain, they're guided by "cellular adhesion molecules" to their target and apply a neurotransmitter specific to their purpose or form temporary faux synapses. Their activity is triggered by harmless but artificial chemicals (like food colours, preservatives, artificial flavours...) in fine detail, letting the users of Mother modulate their neurochemistry with an impressive precision.
There are twelve major genotypes of the retrovirus. All variants of Mother that are sold on the market will be some mix of them. The term for a mix of all twelve (cut with glucose), straight from El Nido, is Southern Rainbow.
The White Knights are programmed to die off eventually, meaning anyone who wants to continue enjoying their benefits has to obtain another dose of Mother. Obtaining it is tricky, however - there are mutant counterfeits on the market that have tried to replicate the virus (that's been deliberately designed not to be replicated) to rather adverse effect, resulting in dire consequences for the users, such as "leukemia, astrocytamas, Parkinson's disease, and assorted novel psychoses".