Using rails with existing database or adjusting it

I have a php bot that fill a mysql database, and i want to build a web
app on top of that with rails.
I have te possibility to change the database structure to adhere to the
rails convetions (it is still quasi empty)
If i do that, i will able to use all the rails commodities and
convetions (as if i build the bot and/or database directly in rails) ?
You have other suggestions for, or methods to adjust the database ?
It' s a good idea do modify it to adhere to the rails convetions ? Or it
is the same (i mean, if I modify it i will really able to use rails with
it as if I built it ?).
Thank you in advance.