Thank you so much for your response. I test it, if I have problem with it, say you. tnx.

Do you have other Idea to install Velvet?

"install" a program on Linux consists of two steps:

1. Creating the program's executable file (by either downloading the executable directly or compiling it from source)
2. Adding the location of the executable file to the $PATH variable.

Both apt-get and conda will do all necessary steps for you. IIRC velvet has 2 executables - velvetg and velveth. You can run something like velvetg -h to check if velvet was installed right.