Parrots beak - Gmelia
Likes consistent moisture - take the pot and tree to a sink, flood pot with water. Make sure there are no dry spots. Then let drain, return to windowsill. Every day you want to take your finger, dig into the media past finger nail deep, if it feels moist, do not water, if it feels barely damp, Time to water. If it feels bone dry - you should have watered yesterday. When you check for water, notice the weight of the pot. If heavy, its wet, if light its dry. Eventually your sense of heft will be calibrated by sticking your finger into the media. After a while you won't need to use your finger, you will immediately know if it needs water by its weight. So check to see if it needs water daily, and only water when it actually needs water.
Light. - Indoors it needs the brightest window possible. If possible 3 or more hours of morning sun. Outdoors half shade to full sun. When putting the tree outdoors start it out in shade and every 2 weeks move it to a brighter, sunnier spot.
Potting mix, - it needs a water retentive mix, any standard bonsai mix designed for deciduous trees will do. Purchase a ready made bonsai potting mix from a vendor, one you could use is Bonsai Jack's. You could order a dozen other places. You are in Denver, there is an active bonsai society there that meets at the botanic garden. Likely one or more of there members could tell you where they get their mix. It is not fussy, I would use a blend of pumice (okay to substitute perlite for pumice), pine bark, at the rate of 2 parts pumice, 1 part fir bark. Sift to remove fines. There are a thousand other mixes, many will work. Any "standard deciduous mix" will be fine.
Temperature - in Denver, you get pretty wild swings in temperatures. Bring inside to protect from temperature below 40 F. (4 C) and move it to shade if temperature climbs above 95 F (+34 C).
All in all, pretty easy to take care of.
