Wnat to invest into index funds for retirement how should i go about it.

So ive heard that the safe way to invest for retirement is to do it through index funds and bonds. Currently i am investing 200 a month (and another 200 into my roth and 100 a month into my traditional savings) but how should i go about this. Should i change how much im putting into my roth vs investing and savings and what indexes should i put into