A pic of the overall park showing the default entrance as well as your stuff would help.
But anyway, when you start a new sandbox park, you already have a park entrance gate at the end of the starting bit of path emerging from the cave at the edge of the map. Usually, you can't change much if any of that except to change the path texture/curb settings. You can't get rid of the default park entrance gate and it's rather difficult, sometimes impossible depending on the map, to add multiple new gates of your own beside it. So in general, if you want an entrance building, you just build it around the default gate without adding any more gates.
Anyway, whether you do that or not, everything else in your park must connect to the starting default path. IOW, if you build a ride or shop somewhere within the park, you have to extend the starting default path to your stuff.