1. Create a SSH key (Git bash is recommended):
   https://docs.gitlab.com/ee/ssh/

   ssh-keygen -o -t rsa -b 4096 -C "[email protected]"
   
   //Copy public key (id_rsa.pub is default name)
   cat ~/.ssh/id_rsa.pub | clip

2. Login Gitlab and paste SSH key in account page
   https://hk.saowen.com/a/a94e3743e7b0591aca8b3bd6361ee64c6c7ffae1863c205f0f602f77307537d6
3. Execute clone command:

   git clone ssh://[email protected]:group/repo.git myfoldername
   

   https://git-scm.com/book/zh-tw/v2/Git-%E5%9F%BA%E7%A4%8E-%E5%8F%96%E5%BE%97%E4%B8%80%E5%80%8B-Git-%E5%80%89%E5%84%B2

4. Then you can create a new repo in Source Tree or Github Desktop

Reference:

1. https://yehchitsai.gitbooks.io/linux-usage/content/use_gitlab.html