The DNA molecule is 'unzipped' in the correct place. DNA is transcribed (NOT translated v. important) into messenger RNA (mRNA) by RNA polymerases. In RNA the base thymine is replaced by uracil, but adenine, guanine and cytosine are the same.
mRNA leaves the nucleus and binds to a ribosome, which contains ribosomal RNA (rRNA), which is involved in reading the mRNA code and translating this into protein.
Once the mRNA is bound to the ribosome the code is read in groups of three bases called codons. For each codon (except stop) there is a third RNA called transfer RNA (tRNA) which carries an anticodon which binds to the mRNA codon. The other portion of the tRNA molecule has the correct amino acid. As each codon is read. the correct amino acid is then added to the chain, Once a stop codon is reached the process ends, the new protein chain has been synthesised. The protein-mRNA-ribosome complex breaks up and mRNA is broken down rapidly.
Search genetic code to see which codons specify which amino acid. Also DNA to RNA is transcription; RNA to protein is translation.