It looks like there's not a straightforward solution for HTTPS-based cloning regarding GitLab. Therefore if you want a SSH-based cloning, you should take account these three forthcoming steps:
Create properly an SSH key using your email used to sign up. I would use the default filename to key for Windows. Don't forget to introduce a password! (tip: you can skip this step if you already have one ssh key here)
$ ssh-keygen -t rsa -C "your.email@example.com" -b 4096
Generating public/private rsa key pair.
Enter file in which to save the key ($PWD/.ssh/id_rsa): [\n]
Enter passphrase (empty for no passphrase):[your password]
Enter same passphrase again: [your password]
Your identification has been saved in $PWD/.ssh/id_rsa.
Your public key has been saved in $PWD/.ssh/id_rsa.pub.
Copy and paste all content from the recently id_rsa.pub
generated into Setting>SSH keys>Key from your GitLab profile.
# Copy to clipboard
pbcopy < ~/.ssh/id_rsa.pub
Get locally connected:
$ ssh -i $PWD/.ssh/id_rsa git@gitlab.com
Enter passphrase for key "$PWD/.ssh/id_rsa": [your password]
PTY allocation request failed on channel 0
Welcome to GitLab, you!
Connection to gitlab.com closed.
Finally, clone any private or internal GitLab repository!
$ git clone https://git.metabarcoding.org/obitools/ROBIBarcodes.git
Cloning into 'ROBIBarcodes'...
remote: Counting objects: 69, done.
remote: Compressing objects: 100% (65/65), done.
remote: Total 69 (delta 14), reused 0 (delta 0)
Unpacking objects: 100% (69/69), done.