I’ve read that a tRNA molecule attaches to an amino acid and brings it to the ribosome to match it to a codon in mRNA, but I’m not very sure where to these amino acids are found in the cell and how does the tRNA "know" when it is time to bring an specific amino acid and how does it move to the ribosome.
Amino-acids, either synthetised in the cell or imported from the extracellular medium are everywhere in the cytoplasm. tRNA are
charged with amino-acids by the aminoacyl tRNA synthetases and they are always present. Charged tRNA do not need to know that a codon needs an anticodon. It is just a law of equilibrium. If bad charged tRNAs interact with the codon presented by the ribosome they are not bound to the codon. Only when the complementary anticodon arrives it remains bound on the codon because of their mutual affinity. On Utube you will find animated videos which are very pedagogic on translation.