Okay, lets start with the original gene.  Genes are sections of amino acids, grouped together in threes to make a unit called a codon.  These amino acids consist of a sugar, phosphate, and a base.  The bases in DNA consist of four bases: adenine, thymine, guanine, and cytosine.  So to start, we need a section of DNA, which can be arranged in whatever pattern you want, since you are "making" your own mutant dinosaur.  How about this one:

CAAGCGTTTATA

Messenger RNA (mRNA) is what is used to go get the necessary codon units to build new DNA.  The bases are the pairing opposite of what the DNA is in the original strand, because adenine pairs with thymine, while guanine pairs with cytosine.  The only difference in mRNA and the DNA it codes for is the base thymine is relaced by the base uracil, so every where there is a need to code for a "T", a "U" appears.  The mRNA for this strand of DNA would look like this:

GUUCGCAAAUAU

Now, on to the mutations.  Insertion is when a new base is inserted, as an "extra", so pick anywhere you want in the original DNA sequence, and insert an A, T, G, or a C, like this:

CAAGCGATTTATA

Deleting is when one of the original bases is removed, or deleted, so pick one of the bases in the original strand, and remove it, like this:

CAGCGTTTATA

Finally, substitution is when you take one of the original bases out and substitute it with another base, so pick a base from the original strand, remove it and substitute it with one of the other three bases, like this:

CAAGCGTGTATA

There you go!  Consider your dinosaur "successfully mutated"!