If you have a CPU, RIGHT NOW, that works in that motherboard, then yes, you can upgrade the bios to the latest, or whichever version is newer than when the support for the 7th gen cpus was added to the microcode, and afterwards run any of the 7th gen Kaby Lake CPUs that are supported.
You must have a 6th gen CPU to do that though. If you do not, then your choices are as mazboy explained, limited to taking it to a shop that has a six gen CPU and can do it for you (Probably not the cheapest option ever), finding somebody ELSE with one, that will let you use it to flash your bios, or sending it in for factory flashing, which will probably also cost you at the minimum for shipping.
Bottom line is, if you have a CPU that runs in that motherboard NOW, it's probably not the best idea AND there is not going to be an awful lot of difference, if any, in performance between a higher tiered 6th gen CPU and an equivalent 7th gen model. If you have a 6700k there is no sense upgrading to a 7700k. If you have a 6600k there is no sense upgrading to a 7600k. If you have a Skylake Pentium it makes just as much sense, in most cases depending on cost and availability, to update to a Skylake i3, i5 or i7 than it does to go through the hassle of upgrading to a Kaby Lake model and all the bios issues with flashing if you don't have a suitable CPU already.