Please answer in two days.
Each isomer is to be considered as a separate and individual compound and named accordingly.
Like CH3CH2CH2CH3 is the isomer of butane.
Name it has any other organic compound. Consider the longest chain which has 4 carbon atoms. Hence it is butane. But because it has 4 carbon atoms and ane because it is an alkane.
Now , how to make structural isomers.
See the best way to draw a structural isomer is to see how many carbon atoms the formula has. suppose 6. Then the various chains possible will be:
First isomer is always the straight chain:
Second set will be one branch with all possible positions:
Now for two branches: These two branches can be on the same carbon or different carbon.
And it can be other chains possible also. So, basically while drawing a structural isomer draw the carbon chain skeleton first and then see how many these are possible. It can have straight, branches or rings as well if it satisfies the molecular formula. Then in the end complete the tetravalency of carbon by hydrogen atoms.
For position isomers , you can make them with different positions of double bond, triple bond or functional group whatever is there in the compound.
Hope it clarifies your doubt. Any specific compound , do ask. All the best for your exam!