You need to place a streaming area in your room first. You can do it in Room customization mode, press R, you'll find a rug icon there. 'Look' at the rug after placing it, press R, buy a sex machine. Click Select, It'll spawn the sex machine. 'Look' at the Sex machine, press E, attach a toy. That's it, you can use the machine in masturbation mode now.
If you want to masturbate without the machine, press Tab in Masturbation mode, pick a toy. Hit the spacebar to see what options are available.
In Master mode, press Tab, choose a different position. Default position doesn't support anal.