Here is how I would break it down, in order:
You are to write a "compiler" for the language, E, which is an expression-based language. I'll describe what E is once you contact me.
1. Make sure that symbol table is working correctly at least within the single scope of an E program.
2. Get Flex input file to recognize E tokens
3. Get a grammar to recognize E expressions.
4. Put the grammar of 3. into Bison input format and test the grammar with no actions to see that you are "accepting" E programs.
5. Add in the actions for everything except exponentiation.
6. Add exponentiation.