Rule 1 :- The longest chain in the molecule will be the parent chain. So, the first thing one should do is to find the longest carbon chain in the molecule.

Rule 2 :- Find out all the substituents present on the carbon chain. It can be any- from methyl to any alcohol substituent.

Rule 3 :- Start numbering the parent chain from the end such that the substituent gets the lowest number. This is called the lowest locant rule.

Rule 4 :- If the substituent occurs more than one time, then the prefix di, tri or tetra is being used with the location of the carbon on which it is present.

Rule 5 :- If more than one substituents are present and they are different. So, these will be named in alphabetical order.

In the given compound, $\mathrm{Br}$ is present at position $2 \mathrm{and} 3$, phenyl at position $1$, parent chain has $5$ carbon atoms.