I want to build a game for Nintendo switch or ps4 but I need to build a pc. Not sure where to start. I know ue4 system requirements but I need more info . I have build a gaming pc before,so I know a lol about pc building.
There are several threads you can find on this forum via its search function or Google.
As far as general PC builds goes, the PC Master Race subreddit has some guides that are decent.
http://www.logicalincrements.com/ is a great starting point, favor a better CPU if you are going to be compiling or baking light a lot. Favor a better GPU is you are going with dynamic lighting and higher end graphics.