How to load my download file(tracks) in RCT3 ?
i have putting those download file under My Documents > RCT 3 ...
but may i know how do i load those file in sandbox mode ?
thankyou

You need to put the TRK files in the Tracks folder in: Documents -> RCT3 -> Tracks.

i already put it...but how can i load it from sandbox mode ?

As RCTgoMatthew suggested, that’s where TRK files would go.

Are you saying you open a park in Sandbox, that you want to build the downloaded track that you put in and are unable to find the ride you put in?

If this is what you’re trying to do, first check to be sure you’re looking for the downloaded ride in the right category when you bring up the rides menu. Just like with CS, if you’re not sure what category to look for it in or if it’s not showing up in the category where you think it should be you’ll may need to check every ride type in every ride category.

Look at the TRK file and find the word in brackets. For example, [Extended]Name.trk. The example says Extended, so find the extended coaster in-game and find the little folder in the corner. Click on it and select the track.