indirect indexing looks like this:
But a few assemblers use brackets instead of parenthesis.
What you'd do to use it, is put the address to your nametable data in 2 bytes of zeropage-RAM. We'll call them addr_lo and addr_hi. You'd do that (in most assemblers) like this:
lda #sta addr_lo
That's the 'indirect' part. The indexing part uses the Y register, and is an index into the address that we have in addr_lo,addr_hi
A way to use it would be like this:
ldx #4 ; (load 256*4 bytes)
See how that works? Indirect indexed mode is also useable with several other instructions, it can be really useful.