Here is a link to the manual for the receiver.
https://docs.sony.com/release/strd915.pdf
The speaker terminals are clearly labeled. You will set the receiver up for the combination of speakers you have.
The turntable connects to the phono input.
The CD player/ recorder would connect to the DAT input (the out of the CD goes to the in of the receiver for playback, out of the receiver goes to the in of the CD for recording.
The cassette connects to the tape deck in and out.
The EQ would not be useable for controlling the tone of the speakers since you have multiple channels and the EQ is 2 channel. You could connect it to EQ one source for playback and the recordings by connecting the recorder to it. Here is a manual for a similar model...