Need to send it to a gunsmith to install it. You will probably not be able to do it yourself as it involves milling out the lower receiver so the sear will fit and then drilling holes for the sear pin. I've heard the hammer needs to be welded and modified to work with the sear too. If you have a machine shop and trust yourself enough to not screw up the receiver or other parts, go for it.
If you want the 3 round burst option you will need to buy the burst parts and have a gunsmith install that too. Semi FNCs are going for about $2700-3000 lately. Installation of the sear usually costs around $600 as well.
I sent my FNC to Ohio Rapid Fire for the 3rd burst kit installation, they said they could install the burst for $85 and remark the lower receiver for auto, burst, semi, safe for $125.
Unless you already have a semi FNC to convert would be less of a hassle and probably cheaper for you to just get a full rifle with the sear and burst installed.
