Need help with bayonet style connection

I was wondering if anyone can help me out with trying to add the three bayonet syle connections on this boss in the picture below?  I tried a couple times but I just can't wrap my head around how to do it.  If someone could expalin exactly how they would do this it would be mush appreciated!!  I have attached my model so far.  I am still on SW12.

Thanks in advance,

Chris

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