You can hire a bicycle and go there on a day trip or spend the night in Bhaktapur. Depending on type of bicycle and number of days, it will cost something between NRS150 and NRS 600.
Of course a motorbike is more expensive.
A local bus is extremely cheap (NRS 20-30) and can be very interesting for a foreigner, but for some people this is a little too much.
A taxi might cost you around NRS 500 one way.
As the statue is pretty tall you will easily find it. In case you want to check some pictures on Google Earth, the exact location is: 27°38′46″N 85°28′27,5″E
For your comfortable and relaxed visit, I suggest you to take a taxi or rent a motorbike.
A taxi may charge you around $7 to $8 one way. You can start your journey from Thamel, Sundhara or Bus park. It takes around 45 minutes to get there from Thamel.
You can even hire a motorbike from hiring centre. It may charge around $7 to $14 per day depending upon the type of bike you choose. It takes you around 30 minutes to get there on bike. Here are some of the bike vendors.
Singh Motorbike Center +977 01 4418594
B.S. Motorbikes +977 9851064164
You can even choose a public transport since they are the cheapest of all but less comfortable. You can get daily buses from buspark. It takes around an hour to get there. It charges you around 40 cents.