I got this table and legs from IKEA, and I have no idea how to assemble them.
The legs are like this:
The table has screws on one side
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Looks to me like you have a GALANT leg. From IKEA's website
The legs shall be fitted on to the frame before the table top is put in place.
If you only have the table and legs, you may not have everything you need.
Based on instructions found at the customer service site linked to by alt, you need to put the legs onto the frame bar piece, then put the screw through the top of the frame into the hole in the leg. Then attach the table to the frame with additional screws (smaller than the ones in your picture).