Congrats...if you walked or biked this far enjoy the scenery along the river, take a rest at the firepit and then go find the relatively easy to find cache container. First to find gets a Trail sticker and a mini compass. Please replace as found and bring your own pen.
If you park at Trailhead M this is appx 1.75m one way walk. If you want the FULL experience of the BTC, park at Allison Park. You are looking at somehwere between 5-6 miles roundtrip depending on which actual routes you choose to take along the way.